rear tires not centered in body

I have a 8.75" rear end out of a A body in a 69 Dart. trying to use 15 X 8 with 4.75" back spacing.
Tires are 255/60-15"
My problem is the left side fits, but tight, the right side is 5/8" out. It is 5/8" towards to fender, into the lip. The rear axle is centered in the body, the disc brake kit fits the housing and rotors, the axles have the green bearings, so they are the correct length.
There is 3/4" between the tire and the leaf springs on both sides. I have double checked the measurements of the body and they are the same side to side and the rear quarters look very straight and the trunk and doors have the correct gaps.

This is driving me nuts, was wondering if there are any ideas? I thought about getting a 5" backspace just for the right side, but nut sure if it would look good or even help.

Any suggestion are welcome.
maybe a quarter panel was replaced,and wasnt just right