Two things you can do on converting the early A body small 4.0 bolt pattern axles to the 4.5 bolt pattern, you can have your axles drilled for the 4.5 pattern and use screw in studs or buy new 30 spline axles for the stock A body housing axles and stock 1 3/4 size brakes and have the O.D. of the axle outer mounting flange cut down to clear the stock 1 3/4 brakes drums and use the stock parts or buy a set of 10.0,10.5 or 11.0 backing plates and drums and used them with the new axles set up for the standard B,C and E body 8 3/4 rear ends
Your choice