What's the widest wheel and offset that will fit on 68 cuda

autoxcuda said
That makes sense to me.

LBP 8 1/4 is tiny bit wider that SBP 8 3/4. And the 4.25 backspace pushes the tire outward a little too. Most 15x8 rims are 4.50" backspace

Think you've got that backward. LBP 8.25 is ~56.75" drum to drum, even the SBP 8 3/4 is 57.125".

Still makes sense though, you'd need the 4.5" (or more) backspace on the 15x8 with the 8 3/4 to put the tire in the same place as the 8.25 with a 15x8 and 4.25" backspace.