Suggestions: 1) For research, suggest you visit your local library and ask a reference librarian to help you look for magazine articles and reviews in the "Readers Guide to Periodicals." This is an index of magazines. 2) Also, have you tried asking Audio Research? They probably have copies of articles and reviews, and might be willing to refer you to magazines and dates you could look up. 3) If you think there's a need for an Audio Research site like you describe, why not create that yourself?
ARC product history (Audio Research)
I'd like to learn more about the manufacturing dates and specifications (not to mention reviews) of ARC's product line, going back some years. Their website is great, but only covers the current line-up. Are there any ARC enthusiast pages out there? Or other good references?