You most likely have a 722.5 transmission (like the 722.3 tranny but with an over drive-installed on 129/140 cars with the I-6). In the later part of 1996, they started installing the 722.6 (the most recent electronic controled 5 speed tranny) only in v8/v12 cars (if I remember correctly). You are correct about 1997+ cars are equipped with the 722.6 electronic transmission. Hope this helps you out.

C.