0" offset on a 12" wheel would be 6.5" back spacing. 12" is nominal / bead to bead size, actual edge to edge width of a 12" wheel would be close to 13". Backspace is measured from a flat surface, edge of the wheel; offset is measured from centerline. If you need to push your wheel out a little have your friend make you a hub centric spacer that also centers on the axle register. It will be OK as long as your studs have plenty of length. You can run 3" studs on yours with open lugs, they will be under the caps anyway.
