1966 Mustang quarter panel issue

[Forder]

I had a quarter panel replaced on my 1966 mustang fastback. Since that happened I've had issues with the tire rubbing the quarter if I hit a large bump. I'm trying to determine the source so I can fix it. It does not rub on the side with the original quarter panel, only the side with the new quarter panel.


There is a flat lip that runs all around the opening for the rear wheel. This flat lip on the reproduction quarter panel is 1 1/4" That same lip on the other quarter panel, which is a original quarter panel is 7/8". Can someone measure their mustang that has original quarters and tell me which is correct ? Attached are pictures.


Also that lip on the original quarter panel is flat/parallel to the ground/tire. The lip on the new quarter has a slight angle to it. Which is correct ? Attached are pictures


I'm also trying to determine if my rear springs are sagging. Measuring from the middle of the wheel. From the ground straight up to that lip I referred to earlier is 25" on my car. Does anybody know what that measurement would have been on a brand new stock 1966 v8 mustang ?


If my rear springs are a issue, where is the best place for replacements ?