Did they use different styles of Seat brackets? I've had a bunch of 3rd Gens, and some the seat slid back further than others. thi is an issue because I'm 6"5', and my knees are in the dash. If memory serves, the difference may be T-tops and Convertibles, Vs hard tops, or it could be IROC vs lesser models. I've owned 27 3rd gens, and they kinda run together after awhile.

 

The power driver's seat goes back about 2" farther than the manual driver's seat. This may be the difference you're thinking of.