B body 8 3/4 in an A body

Thanks guys, I did some measuring tonight and my BBP wheels have 3.5" backspacing. Basically they will fit in there without any room to move. Which is obviously a no go. I think 5" backspacing is what you need if you're going to use the 65-67 B rear on a Barracuda.

Do you guys know what the minimum gap should be between the tire and wheel well?