You're close.
All A-Bodies built after January 1st 1976 had bbp disc brakes regardless of engine or options.
All A-Bodies from '73 to '76 had bbp disc brakes if ordered with power brakes regardless of engine.
All A-Bodies from '73 to '76 V8 cars had bbp disc brakes regardless of power or manual.
All A-Bodies from '73 to '76 340 and 360 cars had bbp front disc brakes power assist only.
All A-Bodies from '73 to '76 had bbp rear ends to go with the front bbp disc brakes either 7 1/4 or 8 1/4 sizes, and all 340 or 360 cars were 8 1/4 only. (They did not make any sbp 8 1/4 rear ends BTW)
If you ordered a car with a slant 6 and manual brakes, you got sbp 9'' front drums and a sbp 7 1/4 rear end automatically from '73 to Jan 1st '76 when bbp and disc front brakes became mandatory.
I hope this helps...............
