On the inside of the wheels near the center of them it has front and back stamped on them. I don't remember if it's FRONT and REAR or like LF (left front) RF. I think it's Front Rear
All GTAs have the different offsets. The backs of the rims are stamped either FRONT or REAR. Even IROC-Zs with the 16" rims have the different offsets. Makes for rotating tires a real pain!
Chris
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1989 Turbo Trans Am #760 (1563 miles)
1983 Delorean DMC-12
1985 Kawasaki Eliminator ZL900
The difference in offset is because of the front calipers, the rear wheels will not fit in the front. Lots of people buy another set of fronts to have the same look all around.