Manual disc brakes vs power disc brakes questions

To reiterate, when I changed ONLY the calipers to the 2.75 bore size, the 15/16 MC that was on the car working for several years, would not move enough fluid to properly operate the brakes. Yes, the pedal did hit the floor. I changed to the 1 1/32 bore, and instant pedal, worked great. End of story.

something was not right with your brakes.I have always used 2 .75" piston callipers with 15/16" or 1" bore master and my a bodies all stopped effortlessly with about 2 1/2" of pedal travel.
i don't know about moving enough fluid...the pistons only move about .003 - .005