There should be no restriction to the front brakes as they do 75% or more of the work , there is a residual pressure valve in the master for drum brakes so you need a different master cylinder for disc brakes . Generally without changing the prop valve or the wheel cylinders the rear will lock up first & easily so they require less pressure .
There is also the issue of matching the right bore size , too large makes the pedal hard to push & hard to get the brakes to work & with limited travel , too small & the pedal travels too far & it is easy to over apply the brakes with excessive pressure .
This is all great in theory but with a customers Camaro we tried 3 different bore masters & no matter how hard you pushed on the pedal the car just would not stop . It had 4 wheel discs & just could not make the brakes work well .
