Yes the 90+ rear interior panels are different mainly because of the rear shoulder belts. The tonneau cover is also different because the space they go in is not the same width. However, it is a fox car whether it's 87-89 or 90-93 so yes you can install the shoulder belts in the older interior and use the newer panels, but the shoulder belt installation might take some fabrication because the provision for it would not have been there on the earlier cars. Or use the newer panels only and fill in the hole for the shoulder belt...