Mini tub Dart wheel sizes

I had a B-body housing shortened to A-body width, backbraced and trued by Moser. It was off quite a bit from the visible offset of the ends welded back onto the tubes.
Anyhow I currently have 15x10 (widened rally wheels with an 8" backspacing), and 295-50R15 tires. It's a bit too close on the inside, especially the left. The more usual 7.25" backspacing would allow 325, I think.