275/60/15 sidewall clearance to leaf spring clamps- suggestions?

How much clearance now with the rear wheel opening lip? Seems to me like it would be easier just to buy a set of wheels with less backspace, and cheaper in the long run than buying a pair of 255's and also buying and installing an offset rear spring kit.

Edit, just checked my file because I couldn't remember what my backspace was, but I'm running 275/60-15s on the rear of my 67 Barracuda, 15x8 Cragars SS wheels, backspacing is 4.25. 8 3/4 rear, instead of your 8 1/4, so not directly applicable, but it clears OEM springs and fender lip nicely.