Converting rear drum brakes from SBP to BBP

Obviously I am confused. I'm new to this and I've been trying to gather information from around the web so any help is appreciated. I'm wanting to convert to BBP in the most cost effective way.

The UCA's have to come from a 73-76 A body equipped with disc brakes? Do all these models have the BBP?

I assume that the spindles, rotors and calipers must come from the same A body?

Do all 73-76 A bodies use the 15/16" master cylinder? What other models should I be looking at?

Why don't you like power brakes on these cars?

As for the rear of the car, any suggestions? I would like to come out with a larger diameter drum in the process.