this has been a thorn in the side of virtually every A body owner I know including me , you cannot service the factory disc brakes even though they do work great , any disc upgrade requires using larger bolt pattern rotors , there is no easy fix , the rear is easier to deal with , you can have the rear axles redrilled & redrill the drums as well or use a similar 10" dia drum off a B or E body 8 3/4 or you can order new axles with the larger pattern , or run a spacer with a high offset wheel . I cannot remember how much tire fits in the rear , both the A bodys I had recently had tubs , I think a 275 will fit with the offset spring hangers . possibly without as well + there are far more wheel choices once all 4 are the 4.5" bolt pattern
