i did the a-body manual disc conversion on a b-body. i ended up with a 1.03 master cylinder after trying a smaller .93. the car stops but not very well. to do it over again i'd never use a large single piston caliper. beware that some kits use a 2.74 piston for b and e bodies. i had to get rid of the 2.74 and go down to the 2.47 to help in stopping. i have another b-body with 11" drums and power assist and i'd never ever ever ever take those drums off for a disc conversion knowing what i know now. there is absolutely no comparison in stopping.