Wondering the same question, putting Sbp 7.25 backing plate on sbp 8.75 and drilling the extra hole.
But as it turns out (from this old thread)
You can't?
Narrowing down a bbp b body 8.75 to a body length but using sbp axels shafts to fit the narrowed housing out if a deamon as I got a.good deal on them and I want to keep my stock steelies which are 5 on 4
So, on the look for sbp.8.75.backing plates now i guess?