[Keith Seymore]

You can also refer to the GM Heritage Center archives and download (free) .pdf files of the information packets for the various years. These reference documents are a compilation of the actual docs that engineering used in order to release parts to the assembly plant.

http://www.gmheritagecenter.com/gm-h...tion-kits.html

In terms of model and option content, and why some models were offered for various years and not others, it is a pure business case decision made by the specific program teams at the time. There's really no way to know unless you were a fly on the wall in the conference room while the discussions took place (or if you can find someone that took really good notes).

K