The front end is out of a '51 1/2 ton truck which had the "Huck" style of brakes. These used a 1-1/4" diameter wheel cylinder with integrated adjusters. Since one was leaking, I figure the best bet was to replace both of them. Believe it or not, the local Napa actually had them in stock.
While investigating the differences in brakes between the years of the AD trucks, I realized that the truck had a larger ID master cylinder than it's 1/2 ton counterparts. Also, the 3/4 and 1 ton version used Bendix style brakes with 1-1/8" diameter wheel cylinders. Since the Bendix brakes are self energizing, the line pressure can be lower than the Huck style brakes. So, what this all means is that the stock 3/4 master cylinder was too big for the 1/2 ton wheel cylinders which reduced the line pressure. This made the pedal feel harder than what it should have been. Napa actually had the correct 1/2 ton master available which ended up being a direct bolt on. Now the brakes work and feel great.
While checking the fluids before the first test drive, I noticed that the rear end was low. As I added gear lube, it ran out as fast as I put it in. The rear cover was leaking and when it was removed, only about 1/2 of the gasket was present. After a bit of research, Autozone was able to order one in directly from Federal Mogul.
With the brakes fixed and leaks address, it's almost done now. I am just waiting on dust caps for the front hubs.
Napa Part Numbers:
Master Cylinder: P29770
Wheel Cylinder: 3406
Autozone Part Number:
Rear end gasket: RDS-4304