I recommend buying a new master cylinder. With the rebuilt, the key work is "if" it's done correctly. I installed a Corvette master cylinder in my '48 Chevy 1 ton, drum/drum brakes. I used '69-'76 Corvette power brake master cylinder even though I run non power brakes. The push rod hole is deep on these just like a manual master cylinder. I don't use residual valves in my truck and it stops great. When I had the residual valves in, the brake pedal was very hard and the brakes were lousy. I tried 3 different sets of residual valves all with the same poor result. 8,000 miles later it stops great with no residual valves. I have a '74-'76 Mustang II power brake set up in my '54 Chevy Panel with disc/ drum brakes. No residual valves. The truck has been on the road 18 yrs now, with no brake problems.
