Ran discs on many cars with no power booster, even on all four wheels... As Jerry mentioned, pedal ratio is important as is the size of the master cylinder. On a light car with disc front, drum rear, a 7/8" or 1" cylinder with the appropriate residual valves and probably an adjustable proportioning valve will work fine... I do, however, always check and set my brakes on a new build using brake pressure gauges to balance the fluid pressure at the wheels...