Backspacing question

And 255s have about a 10" section on a checking rim of 7 inches. But they need at least an 8" rim to handle and wear decently. That would likely bring the section width to 10.5.No problem overall
With a zero offset wheel this would be a 4.5 bs, no problem on the inboard side, but into the outer wheelhouse on the outboard side.Ouch
Ima thinking you might make that work with a 5.75 bs, but it would be tight.
Blu?
Don't be thinking of running that 255 on a 7"rim to tuck it in. You will have to reduce the tire pressure to something like 24psi, to make it run flat to the road. That works in a straight line. But the first time you run it around a turn at 30 mph with the power on, you'll be in for a nasty surprise; namely rear-steer! This is when the tire-tread rolls under the car,taking the sidewall with it. Sidewalls do not take kindly to that abuse. They're only 2 plys and have no carcass protection