Yeah the outer edge of the wheel didn't move (front space on both is the same at 4.5") but the centerline of the wheel moves. You think that moving the center line of the wheel a 1/2" means that the tire will hang over the lip of the rim the same? The center of the tire is moving a 1/2", that tire will overhang the wheel more on the 7" than it will on the 8". It might not be a full 1/2" because of the tire being squeezed a bit more on the rim, but it will absolutely not be the same as with the 8" wheel, the tire bulge on the outside will be significantly more.
Lots of them. Probably at least as common as a 15x7 with a 4" backspace. And more common than a more useful backspace for a Mopar, like a 15x7 with a 4.25" backspace.