I would highly suggest you get under there and measure, measure, measure. 1972, my back rims are 15x8 4.75 back space. It centers the tire perfectly. I'm exactly half an inch from the unmoved spring and unrolled fender. But before I picked those rims and tires. I got under there and measured. First make sure the car is level. Then run a plumbob from the two contact points. The spring and the inner fender lip. Measure between the two. Subtract 1 inch (1/2" per side for movement while driving). This is your max section width on a centered wheel. Now measure from the front plumb bob to the wheel mounting surface. Then from the back plumb bob to the wheel mounting surface. This will tell you what back spacing to get. Don't just "assume" that what fit others will fit yours. For all you know that rear is not original and wasn't centered right when it was put in. Or maybe the springs were moved. Or who knows what else. Make sense?
