Re: Do 295/50/15 fit the rear of 71 Chevelle?
I ran 15x10 aftermarket rally wheels on my 71 with 5” backspacing as bought. I quickly found that the tires rubbed the quarter panel wheel well lip.
I decided to customize the wheels myself and cut the welds, then reweld them for a 6” backspacing. This was OK, but the inside of the rim just barely rubbed the shock itself, not the mount - and I mean so minimal that I left it alone. If I had to do it again, I’d go 5.75” back spacing. 5.5” backspacing would likely have led to possible rub on the outside on that’s particular car. Not all quarter panel dimensions to the back of the wheel well and rear end location are precisely the same from car to car out of the factory.
Another trick you can employ is variable rate springs. They compress as normal for the first inch or two, then get very stiff and harder to compress. I often had folks in the back seat, and this made that a non-issue.