Backing plate offset

First of all thanks to all of you for your info!:)

Regarding my bolt pattern choice: I just wanted to avoid buying new wheels and wasn´t really aware of the problems I´m having right now...

So what would be the best option in my case?
I guess locating the correct SBP-8,75"-backing plates is close to impossible...

Should I get the axles redrilled to BBP and take 10" drums off any other rear end?
If so, could I use the 7,25" backing plates or the ones that came with the Early B rear end then?