Disc brake small bolt pattern. Going to front big bolt pattern

Just grab everything off a 73up V8 bbp Abody car, including the control arms.
I think the BFMJ cars all carry the same rotors and calipers.
As far as swaps go this one is pretty easy.
In ~76, the A-bodies went to the FMJ-body front suspension; but AFAIK the brakes are still the same.

BTW, the KH 4-piston brakes which should be on your car,are great street-rod brakes; I wouldn't be in any hurry to ditch them.
I think it is possible to get replacement rotors for them with the bbp, I mean that's what I have heard.