no big bolt pattern on a-body axle unless its been re-drilled to the 5 on 4.5 wbp

if it has large brakes on it,it has had the axles swaped already or is a B-body 8 3/4 thats stuck in the A-body...which can be done with an early B-body 8 3/4

the backing plates will determin the size drum and shoes you need

any BP-drums-shoes of any B,E,C,truck,car D-60--8 1/4-8 3/4-9 1/4 should work if the axle has the large brake offset

if the axles are re-drilled to 5 on 4.5 wbp,you will need the skinny drums and shoes and have the drum redrilled to the 5 on 4.5" wbp

you need to check the axle brake offset to make sure of what you have first..this will make sure you are not mixing the brake parts