changing rear axle from sbp to lbp

If the OP is going with a shelf aftermarket LBP axle, the standoff is different from the stock a body axles. Therefore, the stock SBP drums and backing plates will not work with a LBP moser,strange, yukon axle unless the axles is specifically buuilt for the A body standoff. Can't just open the SBP drum centering hole and get it to work.

If the stock A axles are redrilled to LBP, then the stock drum only need drilled for large bolt circle pattern.

The A body 8.75 axle standoff is ~2" and the others are ~2 5/16"