1968 Mustang Coupe 17 Inch Rims/tires Question

I'd definitely ask them what they mean by the comment about "modifications might be necessary", it could just be a disclaimer. These guys sell parts that would fit 90% of the cars out there but after 50+ years and multiple owners and who knows what sort of modifications it is hard for them to guarantee no issues.

Before I hit the link I was assuming it was a backspacing issue, when I put 2003 GT rims (17X8) on my '67 I had to use spacers, but the CJ page says it has the correct backspace already. Only other thing that comes to mind is the rubber size, not sure what you plan to run but 245/45-17 fits fine on mine, I can sometimes get a slight rub at full lock while climbing a ramp, but never on a flat surface and my car is lowered.

Bottom line, call them, tell them what all you've done to the car and see what they say.