You will be amazed at what you can still get from NAPA.
I have a 45 GMC 2.5 ton with some similarities as yours.
So far everything Ive done mechanically ive found from Napa. They probably wont be able to look anything up by application, but as long as you have a part number, weather it be a GM number or other manufacturer, they can usually find it.
The parts that you are looking for fit a variety of different trucks right up through the 70's & 80's.
Check for any numbers on your master cylinder. I was able to come up with a master cylinder by the numbers on mine. mine had a Wagner lockheed number on it, and is still available.
With a little digging, I was able to find all the wheel cylinders. the brake hoses, the master cylinder,& all the bearings in the 2 spd rear end.
If you need a hand with part numbers, I have a couple of old GM parts catalogs that cover our trucks.
Do you still have those numbers? I have a 1946 3 ton that needs a complete brake job. And new bearings in the rear end couldn't hurt
