So the car is a 70 Challenger factory with manual drum brakes. Previous owner has put on 72-74 style spindles calipers and rotors. The brakes work fine, but I don't like the pedal so high and effort used for manual brakes. I'm adding a power booster, but am unsure what master cyl to use. Are they all the same power disc, power drum? Are the fittings the same? I was planning on using a 73 power disc master cyl (10-1515). Am I on the right path? Do I need to mess with proportioning valves. They do work fine right now, I just want power and have a 70-74 booster from another car that I won't be using. Help