What Disc Brakes to Use

I like the idea of a set up from a Diplomat. My '75 Swinger has the SBP which I would like to change to a BBP when I do the brake upgrade. What's the best way to do this? I don't know yet if I have 9" or 10" drums, will that make any difference when I make my swap? Especially if I go the Diplomat route? (My car has the /6 so megga big block stopping is not the issue, just better than the non power drums I have now before I give the car back to my daughter).