You need to change the A body backing plates to a B/C/E body (or truck)backing plate. You can use the 10 inch or the 11 inch.
The factory SBP axles have a different offset which is matched by the backing plate. The Moser and most aftermarkets use the B/C/E body offset.
Only redrilled A body axles would work with your stock A body backing plates. In that case you would also need redrilled drums.
By the way, the stock SBP backing plates and axles bring a pretty good price at swap meets and on Ebay so don't toss them!
