Advice Pleas on rear end.

SBP = small bolt pattern 5 on 4 inch circle. LBP = large bolt pattern 5 on 4.5 inch circle.
8.75 a-body rear will bolt right in but those would be SBP only. 8.75 from a b-body mopar would be LBP but is also a little wider. The 8.75 is most popular with the performance minded and can be quite expensive.