OldIHC

I could not hazard a guess on cost, too much unknown. Given the size and weights you are talking, I think my old service truck would be a good approximate to what you can expect. It weighed less and was RWD but had a C-6. Yours is 4WD and weighs more but is stick, I just can't see a 1 MPG gain to be worth the trouble.
The Powerstroke has an oil cooler down on one side of the block that takes room where a 392 has none. Ford fitted the 6.9 and 7.3 to 4WD so I think you would have room over the front drive axle for the pan but don't know for sure.
For less money you might be able to fit, or have fitted an EFI system to the 392, and see some gains and have something that is tuneable to cam or header changes and see the same or better mileage increases.
Nikki used to know of a place that made EFI kits for IHC engines. I don't remember the name.

Found it:

http://www.hamiltonfuelinjection.com/ca ... ction.aspx

There are many that run TBI (throttle body injection) but if it were me, and I was going to go thru the trouble and expense of converting to FI it would be multi-port. TBI suffers from some of the same problems carbs do, and isn't much of a step up. Multi-port is a big step in the right direction and all you see on todays engines. TBI has been kicked to the curb( in the OEM market, no OEM is still using it to my knowledge) .

I have nothing more to add to this subject. I know what works and fits with the least amount of grief.
I am off to my shop to hug a B series Cummins.
I will not be checking back on this thread

First off I want to thank you all for the help.
As it seems that I would be spending more to do this conversion than it would cost to find a really nice 2015 or newer truck (which I can't afford) I will not be changing to a diesel engine.
What I will do is go back to my original plan of just changing the T-34 OD 5-speed to a T-36 direct 5-speed and maybe look into some type of fuel injection.
Thanks again.
James

Not sure you have mentioned it, but are there different gear sets available for those axles? I know my '86 Chevy K30 with 4.10s burned 10mpg coasting downhill with the engine off somehow. True, it wouldn't pull the loads, but 3.73 would be an improvement. Or, an overdrive? I bought a 73 LandCruiser parts truck that had an overdrive installed after the transfer case, so you could overdrive the rear axle only for cruising trips.

No, that doesn't give you an IHC diesel, which would be cool to watch the conversion, and I can spend somebody else's money faster than they can...

I would think you could change gears in the axles. I have an overdrive transmission, but around here you only on level ground when you're going from uphill to downhill so it never gets used, also I don't drive old truck very fast.
I know what you mean about liking to spend someone else's money, it's my favorite kind of money to spend.