Ok I have a chance to pick up on a set of GM rally wheels with caps and rims, for a good price. There is 7" wide 15" with 4" backspacing for the fronts, and 8" wide 15" for the rear, again 4" backspacing.

My problem is the offset question. Any idea what safe offset I need for my 1980 Malibu 2dr, so I don't destroy the wheel bearings, tear wheel bolts off, or scrub the tires?