Disc brakes still not stopping good

Adding a power booster will not help.

They make the pedal easier to push, that's really about it. Yes, on an A-body the bracketry for the power booster changes the pedal ratio slightly as well, but you've covered that and more by using 15/16" and 1-1/32" masters.
I have a small piston master cyl out of an 87 dodge diplomat on my 4 wheel disc set up. it will stop ok (so far) but still requires some leg. think I`m going to extend the brake pedal about an inch, and move it over -more like an auto. brake pedal. ---- thots on this ??-- anyone!