Its a 74 Dart Sport so there's a bit more room in the rear. I remember you mentioning something about 10" wide wheels working better with the A-body rear. Would that work with the stock spring location?
The 10” wheels generally have a better selection of wheels in the right backspace but I really think you need a 1/2” spring offset to make it work. I fit 275’s on my Duster with 17x9’s but they were super tight, on 10’s you’d have to trim and roll the quarters for sure and it would still be tight. Plus unless everything was perfectly centered it would mean having less than a 1/2” to the rim on one side or the other. A tire rub is one thing, hard parts making contact is something else.