What's the tallest tire dia. I can use on 70 challenger without tire clearance problems?
Front, rear, radial or bias ply? The most common combo is 235 front, 275 rear which is a 26/28 combo. This typically does not have interference issues, provided you get back space dimension that keeps things in tight.
I have run 28" front and 30" rear using drag tires. That means they may not be as wide as many would like on the street. 4" on the front and 10" on the back, and they did not have to deal with driveway angles, curb cuts, or other street issues.
Additionally, if you are running a taller tire, construction becomes important as bias ply tires, high tire pressures, heat, and acceleration can make them grow in diameter. If you are marginally fitting at static load, then the combination above could allow them to grow enough to make contact.