(65 Barracuda)What is the largest 15" rear tire I can run without tubs/rubbing?

We moved the springs in 5/8” against the frame and moved the entire assembly rearward 3/4” to center the wheels in the wheel wells.

Still room to run 2-1/4” duals all the way back.

275/60/15 on a 15 x 8 with 4.5 back space.

Tight but alright.