Hy GMTK and guys, most of the conversion kits I have seen advertised use master cylinders designed for Corvettes, Corvettes were full disc brake cars. Drum brakes need residual valves (10 p.s.i.) to function correctly. I assume that the aftermarket suppliers decided to stock/sell only disc brake master cylinders and also sell the residual valves to those installing their kits on drum/drum or disc/drum equipped vehicles. The problems arise when the purchaser of the kit doesn't realize that the residual valves are required for their particular installation and the person taking the order doesn't know what's required, or thinks to ask what type of braking system this kit is being installed on. Other than the non stock bracket required to mount the dual master cylinder in place of the single master cylinder, the parts to convert should be available through your Friendly Local Auto Parts Store (F.L.A.P.S.). If you have a good F.L.A.P.S. you should be able to come up with a system that will be adequate for your application and not require separate residual valves because those valves will be built into the correctly spec'd master cylinder, hope that helps.
