Well, I was all ready to order some new 15x7 Weld draglite wheels for the front of my 'bird and called Summit. Weld said to order 4.5 in backspacing, but the guy from Summit said that 3.5 would be better as it won't set the wheel as far in.
Unfortunately, the front wheels I now have on the car are these tiny Centerlines made for drag racing and the rear wheels are on a Ford rearend (I know, heresy, but that's the way the car is), so I don't have something to measure for sure.