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.
Then you did something wrong.
I've done two a body disc conversions and both work properly. I'd venture to say thousands have been done and work fine. The factory did hundreds of thousands of these and they worked fine.
They key is to mimic the entire factory setup. Not mix and match and delete stuff you don't think you need.
