I don't, but could I suggest looking for issues of Motor Trend, Popular Science & Mechanics, etc., from when the cars were first introduced? Car and Driver and Road & Track (based on my experience living through that era) probably spent less time on the development process and more time on performance aspects of the cars, but the others often tended to include the "background stuff" you are looking for.
Since the new J-bodies were a pretty big deal for the corporation, you might also find useful insights for your purposes in the relevant issues of Business Week, Forbes, the WSJ, etc. There might also be archived press releases and briefing documents somewhere (GM Heritage?)
The SAE may have relevant papers on file.
Lastly, and it's a long shot, but there might be somebody's marketing thesis or something that did all the research you want to locate. A university librarian would be your friend here.
