[ChevLoRay]

If your plan is to remove, then widen and reinstall the wheelhouses, then you will be able to see, and measure while they're out. You will be the one who can see what will happen.

You aren't going to narrow the rear axle, so it's gonna come down to what you see and how much room you have. Doing it yourself will provide you with the info you need and will take away a "he said I could use yada, yada, yada" from the process. I'm not trying to be anal about it, but what you seem to want for info is something that I think you would be in the best position to determine.

I'm running 275-60x15's on my 4-inch lowered coil-spring rear end on 10-inch wide wheels with a 5-inch backspace. There are no issues with the tires coming into contact with anything, yet. They've been on there for the past three years, although not the last year. Since my truck is a '69, the rear axle is an inch narrower than the '70-72. If you have leaf springs, there will be differences in comparison.