Rear wheel and tire size questions

[Blown71]

Hello all I'm new here and wanted to stop in and say hello.
I'm curious about how wide of a tire will fit under the back of my fleet side 71 before I have to narrow the frame. I want to go as wide as possible and I don't mind trimming the wheel tubs in the bed I just don't want to get into frame surgery at this point. My big block is supercharged and traction is hard to find. If anyone is willing to share their wheel and tire size I would appreciate it.