1969 Camaro Tire Help!
 

So i have a 1969 Camaro COPO clone with the skinny bias Polyglass tires. I have been slowly making the car "my own" by getting the 427 totally rebuilt with a ton more power and mechanically the car is perfect but I want to change the tires and wheels and need help with sizing. I want to get a set of Cragar SS wheels for the front with skinny tires and I want to put the fattest back tires on that i can with black steel wheels without having to modify anything. How the hell do i figure out what tires will fit in the rear without having to buy them and hope they fit right?