Drum brakes can be awesome especially at normal speeds. They are self-energizing so as you come to a stop, you usually have to begin decreasing the pedal pressure. I don't know why yours would not be adequate.
I prefer a smaller M/C like a 15/16; It's easier to modulate, while needing a bit more pedal-travel for the same stops.
I like the Mopar single diaphragm booster, and with an adjustable pushrod, you can dial in the amount of boost. It doesn't have to brake like a FifthAvenue.
The discs off an F-body or 73up A-body would work really well on your street combo, and are relatively cheap. To work on a 72, you would need the 73up UCAs
