9.5", 10" or even 11" wheels with 5" to 5.5" backspacing & the right tire combo & rim diameters... 12.5"-13" total section width 29"-30" diameter can fit, with the correct wheel & back-spacing... I had 10" w/315R/15 drag radials &/or 29.5"x12" Hoosiers, with a 5.5" back-spacing on my last 68 RR no rubbing issues, the inner fender tappers much narrower, towards the top, so the lower the car goes the less tire will fit... I have 9.5" Halbrands w/5" back-spacing & BFG TA's P295/50/15's on my current 68 RR HT, it's tight to the outside of the inner wheel well, but doesn't touch/rub... Percy {spelling?} Makes a Tire Fitment tool, for like $69 at Summit Racing, no guessing that way, cheap insurance, to know for absolutely sure, what will & won't fit your specific car, suspension,tire, wheel diameter & stance etc...