I went with a set of Moser custom alloy axles good for 500 HP speced for the A-body with the large brake offset and 5 on 4.5 wbp

was about 299$ and came with green bearings back whan I did my 68 dart

or have a set of B-body axle cut resplined to A-body specs

it put the 7" rim with 4.5 backspace 245/60/15 tire right in the middle of the wheel tub

1/4" clearance at the fender lip(not rolled) and a 1/4" clearance at the tire bulge and leaf spring for a perfect fit

i now have that A-body 8 3/4 in the 85 truck(bolts right in) and tucked 12" rims with 29x15x15 M/Ts in the fenders with the same 4.5 backspace on the rim

1/4" clearance on the fender lip and 1/4" clearance on the tire bulge and leaf spring just like the Dart( I did tub the bed to the frame rails though)

the 73-up A-body with large brakes and 5 on 4.5 wbp used a 7 1/4 and 8 1/4 rear axle with the large wbp/large brakes

and with my 7" rim 4.5 backset 245/60 tire rubed the leaf spring just enuff to eat the white letters off on turns...needed 4 1/4" backset with the large brake/wbp 7 1/4 axle I had