need some info on a bigger rear end

'66-72 A-body for an 8 3/4 rear. Has the same 4" bolt pattern wheels as your '72 7 1/4.
'73-6 A-body for an 8 1/4 rear. Has the 4 1/2" wheel pattern. You'll need new wheels.
Both need a shorter driveshaft and the larger U-bolts and shock plates but bolt right in.
All other rears would need to be narrowed or the use of negative offset wheels/narrow tires to keep them inside the quarter panel.