Drilling rear drums

33IMP said
Depends on if your axles have the big brake offset, or the small brake A-body offset. If the offset is the same as your small pattern axles, you should be good with just drilling your drums.

I'm not sure about the offset you speak of. How can I tell? From what I can see they were stock SBP axles that were drilled for BBP. There are 2 sets of lug stud holes with the BBP ones filled with studs.