[Jack21]

Front: using 235/45ZR17's on 17 x 8 wheels with 4" backspacing.

Rear: using 275/40ZR17's on 17 x 9 1/2" wheels with 5" backspacing.

Works well, looks good, no rubbing or wear problems.

Derivation. Original front MII suspension dimensions and geometry are retained. Just using aftermarket components. Original factory wheels were Cragar 15 x 8 with 4" (split)backspacing front and rear. Kept the same backspacing for front.

Rear is mid-'80's 8.8 Mustang. As rear wheel was widened from 8" to 9 1/2", ideal backspacing was 4 3/4". Since wheel positioning in - out might be necessary to correct tire rubbing, and it would be easier to move tire out with shims than in, aded 1/4" additional backspacing to rear wheels (5"). Turns out this was not necessary, and 4 3/4" would have worked fine. If you're using a wider diff, you'll need to adjust rear backspacing.

17's have no sidewall bulge like 15's, so pose less clearance problems.