Strange Pilot/ hub size on 8.75 Rear drum brakes
You MUST use redrilled SBP brakes with those axles. Those axles are for the SBP brakes, the axle flange offset is different than standard BBP axles. You can't use those axles with standard BBP brakes. Personally, I would see if you can return them. If you're going BBP there is no real reason to keep using SBP brakes and have to mess with having them re-drilled to fit.
This is the real problem you have, SBP axles had a different axle flange offset and therefore the backing plates can't be interchanged. The register problem is minor compared to the offset issue.
***edit***
Fixed, here's the picture
You MUST use redrilled SBP brakes with those axles. Those axles are for the SBP brakes, the axle flange offset is different than standard BBP axles. You can't use those axles with standard BBP brakes. Personally, I would see if you can return them. If you're going BBP there is no real reason to keep using SBP brakes and have to mess with having them re-drilled to fit.
This is the real problem you have, SBP axles had a different axle flange offset and therefore the backing plates can't be interchanged. The register problem is minor compared to the offset issue.
***edit***
Fixed, here's the picture
