Drum/drum to disc/disc proportioning valve

I had drum brakes on my 72 Dart, front and rear. I have switched to front disc brakes and am in the process of rear disc brakes. I still have the drum/drum master cylinder on the car, is the master cylinder proportion going to be the same as disc/disc? Or should I buy a special master cylinder for a disc/disc brake system? I don't know much about master cylinder proportioning and what % is required for which set up. Any recommendations would be appreciated.