Just to go for a counter flow, since I've done a couple of them, whoever you get the rear spring setup from will have some suggestions. Typically they have the same spacing as an 8" from a V8 Maverick, 56" drum face to drum face. Some are also made to take a Nova 10 bolt, 57-8" depending on year. Yeah, not as many ratio choices with the 8" but good enough for what it sounds like you're doing, and there's no modification necessary, it's a bolt in.