On my 1 1/2 ton with the original drum brakes all around, I used a master cylinder for a 66 Pontiac Catalina that also ran 4 wheel drum brakes. Didn't use a prop valve and it drives as it is supposed to (for a 1948 truck),
Scott

Scott Ward

2 1948 1.5-ton Loadmasters
The red one and The snow pusher
1 1950 3100
1 1955.1 Chevy 6500
1 1954 Chevy 6500 2-Ton
1 1955 1st Series COE 5700
1 1963 K20 (454)
1 1964 C10 (350)
1 1951 1.5-ton Dump Truck
1953 and a 1956 Ford F800

Raising a teenager is like trying to nail Jello to a tree!