off set on a stock 72 dart

I'm not aware of any 8" wide Centerlines. I have seen and used the 15" X 8.5" Centerlines that have a 4-7/8" backspacing. They will work with a small tire 235/60/15 or 225/60/15 it's kind of narrow for that wheel and it makes for a tight fit in the fender. See pictures below.

I feel that a 15" X 7" Centerline with 4-7/8" backspacing is the right fit when combined with a 1/4" spacer these wheels fit nicely. Just doesn't have that deep dish look of the 8.5" wide Centerlines