going back to manual disc brakes from power

Even though the caliper increased in size to 2.75 inches in 1976, the master cylinder was 1 1/32 on manual disc and 15/16 on power disc which were the same sizes as the 73-75 Abodies. Info from the 1976 Chrysler service manual.
According to the Chrysler factory service manuals, post 13 is correct on the 73 thru 75 years.
Of course you can use any size master cylinder you like but the above numbers are from the factory service manuals.