going back to manual disc brakes from power

Newbomb Turk said
You were using a 15/16 MC on power brakes??

The FSM is correct.

I prefer manual disc over power anything but with that 15/16 MC on there that would have been uncomfortable for me to drive.

74 dart’s and dart sport (likely all 74 mopar A bodies) with factory power disc brakes came with 15/16 bore. It’s fine.