Hey guy's, I know this post is from January but I thought I'd answer anyway. I have a 68' coupe with no mods done to the wheel openings. I wanted that 60's & 70's look with thin tires in the front and fat tires in the back. Here in New York
state, my rear tires cannot stick out past the wheel opening, so I went with 14X8" weld wheels (four lug) all the way around. I put P205/70R14's in the front and P245/60R14's in the rear. View my Mustang to see the outcome. My only complaint is the rear tires rub the chrome trim I added around the wheel openings. And that only happens when both of my kids are in the back seat and I go over a railroad crossing. I think I can roll the trim upwards inside the wheel opening and fix that problem though. The other thing is, my rear leaf springs are weak from age and I need to replace the shocks. After these tires were on my car and I looked up underneath it...I think I could have ordered a one inch backspace on the rear rims to accomodate another inch to inch and a half of tire without a problem.