Tire Size 68 Barracuda

What size rims?

With 15’s you’re looking at 225/60/15’s in the front and 275/60/15’s in the back if no mods is the goal. 235/60/15 up front has been done, but that’s not really a “no mods” situation.

With 17’s, 245/45/17’s up front and 275/40/17’s out back. I’d say 255/45/17 up front but the lower front corner of the fender would be an issue.

With 18’s, 275/35/18 front and rear can be done, but in the front the lower front fender corner would need to be dealt with. Otherwise probably 245’s up front again.

The wheel opening in the front fenders is an issue with taller tires, gets to be an issue around 25.6” and taller especially with wider tires.

And of course for wheels that will actually let you do any of that we’d need to know the bolt pattern and brakes you’re running. Backspace changes a bit with the larger bolt pattern brakes.