WHAT SIZE DRAG RADIAL SS SPRING '65 DART

I've seen guys get a 255 radial under an early A. It's close but it fits. Gotta get the backspace right. Probably not terribly helpful but I've seen it first hand.

My old '65 Valiant had 245/60/15s on a 15 x 8 wheel, 4.875" bs. They fit but rubbed sometimes if there were large enough people in the back.