I'm trying to figure out what rim best fits the rear of my Dart?

Leaf springs moved up against the frame rail(not under) Stock Axle width.

I remember years ago being able to fit a 28.5 X 9 Firestone under the car with a 7 inch Auto Drag. ( I can't remember the backspace. )

I'm thinking a 15 X 7 3 1/2 back space would work...

Anyone care to share there experience with this?? TIA