OldIHC

I have a few suggestions as to brakes.
Number one is to replace the rubber lines. Should be three of them, one each at the front wheels and one at the rear axle.
Look very closely at the steel brakes lines. Any sections that have heavy rust/ heavy pitting or have rubbed on a frame clip or something must be replaced.
Next, take the front wheels off. I just had the front drums off my B130 one-ton and the brakes appear identical to R100 half-ton.
Mine has two one-ended wheel cylinders on each front wheel.
If the cylinders aren't pitted you can rejuvenate with wheel cylinder kits. However, my life isn't like that usually. New wheel cylinders might need to be found.
Keep in mind these old brake shoes are very likely asbestos-based. Wear a face mask, why take a chance however small?
I've been working on brakes for forty years and I still do one side at a time in case I forget how something went. Try to keep shoes and return springs together as assemblies.
These old return springs scare me. They can snap at any time. I'd look for new replacements.
White lithium brake grease is dabbed on the contact points between shoes and backing plates after backing plates are washed off with soap and water ( doesn't raise asbestos dust).
Finally, after wheel cylinders are rebuilt or replaced, brake hoses replaced, springs replaced, shoes evaluated for thickness and condition you can repack the front wheel bearings with wheel bearing grease and replace grease seal.
I've reused grease seals that looked OK. If they're available though replace them.
Oversize drums should be replaced. Having said that almost every mechanic I know has temporarily reused slighty oversize drums at some point. Keep in mind your antique truck is unlikely to be ever loaded to capacity again.
However, safety is number one here. Brakes gotta be as good as we can make them.
The one ton brake drums on my B130 had "big six" wheel lug pattern and are indeed unusual-looking.
I replaced mine with used R100 front drums. They went right on. I therefore have two "good"( haven't been miked) front drums.
With your low mileage I suspect your drums are OK, though.
Good luck!

great advice^^^^^^^^I'll add this:

if you do need to turn your drums, take them to a guy who knows about old parts hard to find, they don't need to get turned super smooth, some grooves left in are probably OK.

my buddy takes off just enough to get them smooth & true, you go to a young guy he'll most likely crank the cutter to max and go check his facebook status while chewing off way more drum than needed,

eliminating option of another turn at a later date,

as everyone has said, these larger drums are impossible to find.

Very true. I still haven't found new ones for my 71 Loadstar. Best hope now is for used ones that are not too far gone.

So I'm looking at Rock Auto and see that there is an S-130 and an S-132. From looking at the data plate for the vehicle it say S-132. So I am assuming I should be looking under the S-132. Know it should answer it self but just want to be sure

The primary model is S-130; the 132 is just the S-130 with the heavy GVW rating. Most parts books will list by primary model, UNLESS it is something GVW-specific.

on rock auto most everything for R-100 110 120 etc. will work on your truck EXCEPT some brake parts, wheel cylinders shoes seals are the same on front axle, rears on 130s is different,

rock auto is good, but like any other not IHC specific vendor, some of there stuff isn't complete in applications, so if say you are looking for front seal, not listed for R, but listed for L series, it will fit.

as a general rule MOST but not all mechanicals interchange between L, R & S series, so sometime you gotta look a little deeper on their site if it shows N/A.

Going to to do completely redo the brakes. Any other sources than Rock Auto?

Ebay, Hemmings, NAPA online, Kanter,
Right here is a good place to ask about specific things.
Don't think you're gonna find it all at one place as if you own a 2000 Civic.
Shoes are still being relined if you know where to ask or go. Expensive, though.
I would initially be worried about sourcing those weird wheel cylinders and brake springs.
The rubber and steel brake lines are common enough..probably wheel seals, too,
Good luck. Tell us where you found everything.

If a truck has a hydro-vac the HV MUST be bled before any wheel cyls and engine OFF. Next is the cylinder furthest from the HV not the MC.

Many brakes parts can be bought locally,NAPA($),Carquest,Autozone and the like. They will probably have to order them but you usually don't have shipping charges which buying online you do and it can be expensive.

Here's some part numbers which I used the IH parts manual FIRST as online look up's are not always correct.
Front brakes
87912R91 Cyl. assy. LEFT <single end cyl.>
W9695 Dorman
WC9695 Raybestos
WC9695 Wagner

87913R91 Cyl. assy. RIGHT <single end cyl.>
W9696 Dorman
WC9696 Raybestos
WC9696 Wagner

Kit <1 cyl.>
95302R91 IH
3600 Dorman
WK21Raybestos
WK156 Raybestos
WK3600 Wagner

Hose
BH4900 Raybestos
BH3700 Wagner

Rear Brakes
75084R91 Cyl. assy. LEFT
W9344 Dorman
WC9344 Raybestos
WC9344 Wagner

75085R91 Cyl. assy. RIGHT
W9345 Dorman
WC9345 Raybestos
WC9345 Wagner

Kit 1 per cyl.
121387H IH
5355 Dorman
WK54 Raybestos
WK5355 Wagner

IH pn's are for reference only.

If the MC is an issue it will have to be rebuilt,it's used on other model's and I've done extensive research for a good current aftermarket replacement and there isn't one.
I did find kit pn's though;
Kit
121400H IH (1-1/4 bore?)
TM3613 Dorman
MK1 Raybestos
MK3613 Wagner

The HV unit would also have to be rebuilt and it's not a DIY!

In this link there are troubleshooting and bleeding info;
http://www.bepco.biz/Catalogs/vacuums_&_hydraulics.htm