Hy mahlew, was the master cylinder originally for a disc/disc system, a drum/drum system, or a disc/drum system? A lot of the "upgrade kits" use a master from a Corvette which is a disc/disc system, and when using a disc/disc master cylinder in a drum/drum application you'll have to install residual pressure valves (15 p.s.i.) in each brake circuit because the master cylinder does not have them built in, as a drum/drum master cylinder would, hope that helps.
