I have a 97 K2500 7.4 hydro boost brakes. When I purchased it the previous owner upgraded the rear brakes to disc. the calipers for the rear disc brakes are the same exact part number as the front calipers. now I have a mushy peddle. I know I need a new master cylinder with a larger secondary piston for the new rear calipers. I have no idea where to find something like this. Any help or suggestions would be great.

Thanks
Blake

 

why dont you just change to combination valve to the one they use for 4 wheel disc brakes?