[thecatseye66]

Originally Posted by krue

You need a 71 or 72 master cylinder to make it work right. Or some have done the mods and used the later model master cylinders on their trucks.

Thanks Krue.

What modification do I need to do to use the newer m/c? Does someone make a shorter inner booster rod that will work?
The newer m/c has a short dimple on the piston where the rod from the booster meets it, but the older m/c has a recessed hole that allows the rod from the booster to go in an inch or more before it touches the piston.
When I try to bolt the new m/c to the older booster it just presses the piston in before it can even be attached. I tried to use the rod from the newer booster in the older booster but it is too short.