I was going to make a Reply under Richard's thread "67 GTA 289 Coupe, Spring Codes and Markings, San Jose", that it appeared that we had exhausted all of the MPC's and OSI's, and still had questions, as well as bringing in all 1967 applications into the mix (which can hardly be avoided when researching a specific application).. I was going to suggest that the next step would be researching Marti Reports, Build Sheets, and cars themselves. Then I saw your Reply under Richard's Topic (since rightfully moved away on "its own" here), and saw that you had one heck of a start on that, to which I'm sure you would attest to has been no easy task, and you are definitely to be commended for that.
I think it is interesting that your sheet did not include the AE Spring that John posted a picture of, and that we could find no listing of either. Possibly because John's car has an earlier build date than any other of the 289-2V, GT Fastbacks that you have listed ?
Since going through all of the MPC's and OSI's, I have also gone through my 8/66 Sales Brochure, Showroom Options Book, Buyer's Digest, Preliminary Shop Manual, Shop Manual, Salesman's Price Book, Parts and Service Merchandising News, Shop Tips, and TSB's between August 1966 and August 1967, all to try to see if any more light could be shed on this subject. Result ; nothing eye-opening.
All that being said, before some of our readers will, hopefully, provide some documented information to help "fill in the blanks", I have a few questions/comments for your consideration :
1) While I "surmised" that the "improved handling" noted in the MPC's was actually the "Special Handling Package" furnished with GT's only, I could find nothing to confirm this. Did you use Marti Reports, Build Sheets or what in order to confirm ?
2) The above being the case, I find it odd that the only reference to GT's is in regard to the "Competition Handling Package".
3) I think it would be beneficial to add a column for "Spring Assembly Part Number (5560)".
4) Do the dashes (-) in the "H.D. Suspension" and "Handing Package Type" signify " "unknown" or "Standard" ? Possibly a "?", and "Std." ?
5) Finally,since besides "Standard Springs", Springs with the "Special Handling Package", and Springs with the "Competition Handling Package", different Springs were also available with the "Heavy Duty Suspension" Option, I think the column you have noted "H.D.Suspension" is confusing. While you apparently haven't come across any with just the "Heavy Duty Suspension" yet, it was an Option and this could cause confusion "down the road". Possibly this could be noted "Type of Suspension", or something similar ?
Again, thanks for all of the work you have done on the document to this point. Hopefully, by Posting it mow, others will be able to furnish you additional information to reduce the burden on you, and get closer to a complete document.
Bob