Steel wheel back space

When I talked to Wheel Vintiques they said 5 1/4" max BS for 15 x 7" wheels and 5 3/4" max for 15 x 8" wheels. I got the 15 x 7" with 5" BS for my B body rear. With the extra 1/4" they would have been perfectly centered between the fender and the springs but they are fine like that. With a Dart I bet it's going to be tight with 8" rims. Your conditions may be different but on my 72 Swinger I would need the 5 3/4" BS to fit 8" wheels. 1" wider = 1/2" more BS. Good Luck!