PTO Winch Advice Needed

A lot to unpack in that post.
1st let me say my electric winch use is limited. I used one on an in bed tow truck 40-45 years ago. I never remember a problem with the winch and it was used every day. I don't remember the spec's on the winch or the maker, but being that is was 45 years ago it wouldn't be much help.
The other was a light duty (Warn if I remember correctly) that was used to spin and self unload 12' diameter spools of broadcast coax at remote transmitter sites. It worked well but was only used very infrequently.
The tow truck had a std Ford alternator that needed to be overhauled or replaced every few months from the hard use.
If you are going to work an alternator hard, you need to go brushless, and get one that can handle a high duty cycle. (more on that later)
Battery chemistry and construction will determine the best charging protocol for the battery. Mixing say sealed AGM and flooded cell batteries in a bank will cause one to be damage and one to be undercharge. Lithium batteries should never be paralleled with lead acid.
A deep cycled battery needs a different charge protocol than a starting battery, and just paralleling it with the starting battery will not fully recharge it. This presents a problem for what you want to do. The solutions go from relatively inexpensive (coupla hundred) to the sky is the limit.
The best way is to separate the starting and running electrics from the deep cycle electrics. On two of my trucks, I did this with air start for cranking and everything else run off the deep cycles. Not an option on the Loadstar. On one of my trucks I didn't have room for the air starter tank, so used a Maxwell supercapacitor for cranking and everything else ran off the deep cycle bank. By not using a battery for cranking, it allowed me to optimize the charging for deep cycle service. Also my engine useage (running for 10 hr or more at a time) was ideal for recharging deeply cycled lead acid batteries.
Unfortunately, i don't think the super capacitors starting modules are made any more, they cost over $1000 when I bought mine and were a hard sell to make to most people. So I think that option may not still be available.
The most cost effective option would be two alternators and electrical systems. You would leave the stock system and starting battery as is, and add another alternator and charging system to deal with the deep cycle pack. This allows the starting battery to be recharged as a starting battery and the deep cycles to be recharged in a manor ideal for them. It would also allow different voltage for the deep cycle pack. You mentioned 24 volt, A lot of inverters and stuff is made for 24 volt, so it does hold some advantages, as well as lighter ga cable for the same work (lower amp draw).
A deeply cycled battery pack is going to take a lot of time to recharge under the best conditions, and there is no way to make the process fast, you can make it faster, but still time charging is the key. Mutli stage voltage regulators work, and work well, but time is still the key. Huge alternators don't speed up the process much, and many high output alternators can't handle running at max output for hours at a time.
On my trucks I used the Delco 25SI and 26SI alternators exclusively. They are 75-85 amp but can run 100% duty at that output. They did need modifications to add an external multi stage regulator, but did a great job. The 33 SI and 35SI or any brushless alternator would likely be a good choice. Leece Neville (Motorola- Prestolite) and NIpondenso all sell HD brushless alternators. All will require internal modification to run a multistage regulator.
There are also DC to DC charging systems that will hook to a 12 volt truck electrical system and will multi stage charge a deep cycle bank and the voltage of the bank doesn't have to match. In otherwords 12 volt input from the truck can multi stage charge a 24 volt deep cycle pack.
The cheapest solution and the ones that will give the poorest results just tie the deep cycles to the starting battery in one form or another. either with big diodes or with a solenoid (high power) relay.
DO NOT think you can put two batteries in series and pull power off the center tie and recharge by passing current through both batteries. In otherwords place two 12volts in series to get 24 and charge with a 24 volt alternator but also pull loads off just one of the batteries for 12 volt loads. This will kill both batteries. I can explain why, but it would take a lot of words, just trust me!
Cost wise, the simplest and cheapest would be the solenoid tie of the two banks together, about $50 in relays and such.
The most expensive (but also simple to hook up) are the DC to DC charging converters, your talking over $1000 for the units alone depending on how much current and how many banks of batteries you want to feed.
I think in your case the best bang for the buck would be if you can fit another alternator so you can have one for the truck and its electrical needs (starting ign etc) and one for the deep cycle bank. Cost wise, the making of the alternator mount and belt drive is going to be the tricky part, but if you are a good fabricator and can lay your hands on the needed steel to make the mount, it shouldn't cost that much. Used or rebuilt alternators aren't that expensive, I think the most I paid was $145 for a 25SI. The multi stage regulators are now going for around $200 and you'll need a little skill to modify the alternator, but I think you could yourself. Obviously, you need 24 volt units if you want to run a 24 volt deep cycle pack. The multistage regulator I used could be used alone, or with the original internal reg re-set to "float" voltage. I found that it worked best when hooked with the original as it tended to overheat and shut down when it had to carry the full load. A larger capacity regulator (more expensive) would be another solution, but I liked the idea of a fail-safe back up.
None of this addresses what winch, but I can see the advantage to either P/S (hyd) or electrical for a front mount. Only you can make the choice for you. Both have advantages. Unless you are pulling whole tree trunks, my guess is 3/8" line (and plenty of it) would be enough, along with snatch blocks for the tough pulls.

write up of the Delco mods on pg 7
viewtopic.php?f=36&t=6286&start=60

A lot to digest in your post too.
A quick search shows Maxwell supercapacitors is alive and going strong. Except they now have so many different options for vehicles and other uses I would have to call them to see what they recommend. And it appears their prices are about half now, although I'm not sure that what I was looking at would be the appropriate selection for this application.

Unless I can find a 24 volt regulator that will independently and properly charge both a 12 volt and a 24 volt battery, I agree two different alternators would be the easiest and possibly the best (most dependable and least expensive) way to go. Any idea where I might go to find such a regulator, if it exists?

Otherwise two alternators sounds like the simplest system for me. Don't think any fab work is needed. I can use the AC bracket from a Scout 345 engine to mount the two alternators. That bracket both mounts the standard alternator and provides a flat surface for the AC compressor. I could drill and mount a larger 4-bolt alternator like shown below to that AC bracket. It looks like that would work out easy, although I've only seen pictures of that alternator on google and pictures of the bracket on some of the Lightline dealer web site stores. I have not seen either in real life.

But that also brings up the issue of the 24 volt battery. Should I use a deep cycle battery? I don't know that I would regularly be running the truck long enough to recharge a deep cycle 24 volt battery. What battery is usually used in big trucks? Normally the alternator will supply the current needed for headlights etc. Only when the winch is in use will I be tapping into the battery's energy supply. But then I will be tapping it big time. Seems like more of a starter type of battery should be used for the 24 volt battery, not a deep cycle battery. Your thoughts?
In searching 24 volt batteries on google all I see are Lithium Ion batteries for big $$$. What do you consider the best non-Lithium Ion battery brand and best regulator for a 24 volt battery? Or is Lithium Ion the proper way to go for truck batteries these days? And how many amp hours should I be considering? I don't know the brand but the 24 volt truck batteries sold at Walmart have a lot of very poor 1-star reviews.

Typical 4-bolt alternator for AC bracket:

That alternator is a"pad" mount, but isn't flat on one side. It is possible to make a duel voltage alternator but it is not the regulator that makes it so. The AC voltage is run though a set of three transformers to double or half the voltage (either way will work) and give an output that is double or half that of the standard alternator.
That works ok when the needs of one voltage are small and most of the needs are of the other. Output of the 2nd voltage provided by the transformers are limited to how much current the transformers can handle. In most cases it is only 10 amps or less.
Starting batterys may be sealed or may have removable vent caps, but are made for a quick high amp burst. Deep Cycles flooded cells will always have removable vent caps. I would use Deep Cycles for non starting (or even starting) use.
The Maxwell ESM, was made for engine starting and is in the footprint of a Gp 31 battery (the starting battery used by almost all big trucks) and is more than just a supercapacitor, it is a S/C with a charging board and isolator all built into the ESM. It includes cell balancing devices in the package.
For your "deepcycle side, I would assume it would also run "hotel" loads while camping. It can be 12 , 24 , 32, 36, or 48 volts but 12 would be the most common followed by 24.
Truck alternators generally run 2 V belts or a multi-groove belt to handle the load. I'm not sure a single V could carry the load and not slip.
What ever voltage you decide on for the deep cycle loads, the alternator should also be for that voltage. The internal regulator (if it has one) and the external multi stage reg would also be for that voltage.

My alternator has a double pulley and runs a double set of belts now. I would just get a longer set of belts to spin the other alternator too. Hopefully they make the same type of double pulley for that alternator. Do they make different diameter pulleys and if so, what size would you recommend for a 345 v8?

Ok, the second battery will be a deep cycle battery, and 24 volt. I can't really see doing all this for the same voltage. Otherwise I would just get a 200 plus amp 12 volt alternator and another 12 volt battery and be done with it.
Apparently a multi-stage regulator is appropriate and recommended for a deep cycle battery. Is there any particular brand / model number / source you can recommend for this 24 volt application? I don't know that the guy in the auto parts store would have any idea what I need if I just ask for a multi-stage 24 volt Sterling regulator. I have only scanned that link you left previously, but you know I will carefully re-read and study it at least half a dozen times.

And when you say the type of alternator I showed is "pad mount" can't I just get four spacers or nuts to offset it some from the flat bracket, or is there some other mounting reason why that would not be recommended? I need that style for easy mounting of whatever 24 volt alternator I use.

I assume modifying the alternator will void whatever warranty it has? I'll see when I get it later this year if I really understand the changes to be made. If not, would you be open to letting me pay you to make the changes for me?

Once my choices of power source is sorted, then its back to finalize the winch selections.
Thank you again, Sir.

Ok, lets un pack this a little at a time.
1st look at all the loads you would use on a deep cycle battery bank. For example, winch, we know that, how about camper stuff, lights, heaters, fridge, bunk warmer, etc? If you run any of those 12 volt is more common than 24 volt in North America. You need to know what voltage would be of the most use to you.
You could likely run both alternators off the double pulley as it is unlikely both will be maxed out at the same time.
Yes you could build spacers and space the pad mount alternator enough to mount it to a flat plate. Be very careful when you are building the mount to make sure the pulley is in alignment in all directions with the crank pulley.
I would not buy a brand new alternator to modify, I would buy a used or at most rebuilt on. Yes modifying will void the warranty.
Pulleys are available in 1,2 3 or more grooves and different offsets and diameters. Most truck alternators have a 7/8" shaft
Brushless alternators need to be spun a little faster than brush (revolving field) types. The smaller the pulley the less power it can transmit, so you want to seek a balance between speed and power.
You can buy direct from Sterling USA (https://www.sterling-power-usa.com/) or from Marine suppliers like West Marine. Autoparts store will have no idea what you are talking about.
If you use a pad mount, you need some way to tension the belts, not a problem if you use the OEM alternator on the same belts and it has a tension arm. How much "wrap" the belt has on the pulley also effects how much power it can handle, more wrap= more power. Generally the max for V belts is around 180 deg of wrap, but once you get less than 90 deg less power is available.
To use a Sterling or other multi stage regulator (Balmar etc), you really need to understand how the alternator works and how the regulator work to be able to hook it up. It also helps when (if ) you need to resolve any problems. With the Sterling there are 4 wires (besides the output terminal) that have to connect to the alternator, plus a sense wire to the battery pack and (optional but recommended, comes with the regulator) a temp sensor on the battery.

A word of caution on the newer Delco alternators, anything newer than a 25 SI uses the white "triangle" IC regulator. These are "pre set" and not adjustable. You want to be able to adjust the internal regulator down to "float" voltage (min voltage setting of the multi stage regulator) It is hard to find these white triangle reg in voltages low enough. IIRC I found one that would go as low as 13.6, you may find some aftermarket adjustable ones but I have no experiencing with them and can't recommend any brand. The 25 SI has an adjustment "pot" on the board, and you can dial it anywhere in its "range", which is why I used 25 SI alternators. They are old school. If the internal reg is higher than the multi stage reg on its lowest stage, the charge will never taper fully and will cause the batteries to boil. (use water).

Hi, I'm sure I'll have lots more questions. But in looking around I can't seem to find any 25SI alternators. Are you sure you did not mean a 23SI alternator? I can find them in both a 12 and 24 volt brushless pad mount configuration. In 24 volts they are available in both 50 and 70 amp ratings. Will I be able to modify a 70 amp 23SI pad mount alternator like discussed?
Also what is a J180 hinge? Is that the mounting system of a 3-tab alternator like I'm most accustomed to?
Sorry for all the questions but thank you, Sir, for your help.

https://www.napaonline.com/en/p/WIL90013158

When it came out in the late 60's early 70's (I don't know the exact date) it got the nick name "gray ghost" because it would outlast the engine. It was made to replace the 55 amp generators which were the mainstay of heavy trucking before alternators.
The later 3xSI alternators (30SI 33 SI etc) are based on its design, but use the "white triangle" regulator, and more modern diodes in a replaceable block. The 25 SI used individual diodes press into the case and a insulated frame.
very little to go wrong with them, which was why I picked them up used and modified for my use.

Thank you, Sir.
Was the 25SI ever made in a pad mount version? That's what I meant when I said I couldn't find any. If not, and if the 23SI pad mount can't be modified like you can the 25SI, I can still make the 3-tab 25SI work. It just won't be as simple as drilling 4 holes in the flat mounting plate.

The 25SI was designed in the 60's and was already phased out by the 80's long before the "pad mount" came out. Pad mounts are generally used with multi rim serpentine belts (but not always).

I have a spare, already modified 25 SI, it has a small chunk out of the fan (easily replaced if it causes a problem). and a new double groove pulley. I have to look to see how much I have in it, and what would be a fair price. However, shipping is likely to cost as much as the alternator it self. Last time I had a smaller alternator shipped from Calif to Iowa from another member here, it cost $90 and that was some years ago. Right now I have no way to test it, to make sure the internal reg is working but I believe it to be so. It is a 75 amp 12 volt unit.

I kept a spare in the side box of the truck I was running because I had an alternator go bad (long before I was using the Sterling and modified alternators, just std system) and it cost me over $450 to get it replaced on the road. That was about 20 years ago, and I swore I'd never pay that again. This one has bounced around in a side box for years but never used.
When I get my Marmon dug out of the barn, I can fit and check it, but that will not be for some time. I have the rear suspension apart for frame painting, and until it is back together I can't swing the hood open.