Jeff,
You and Charles have done so much for me in getting started in my build sheet niche of the hobby. Make no mistake, I'm very gratful.
I think that's it's unfair and unrealistic to burden you both, and the other experts that frequent here, with the multitude of questions that can come up during a typical restoration. You have "trained" me to begin to question the veracity of information by continually asking questions like: which plant, what build date, what options, etc. This is good and it relieves the burden off of you and Charles some. Train us what to look for and how to go about looking for it, and we can have hundreds of eyes out there performing the research.
Lacking a more appropriate starting point I don't see a problem with starting with the MPC. That's just me and my thinking. We still need to valid any assumptions, even this one, with real world evidence. Gary has offered his observations (thanks Gary) and that helps confirm one little piece. But in this case, we need to maybe have a checklist of all the particular variables as utilized by the MPC. Gary has given us the facts about the transmission type, body style, steering type, and AC or not. We might assume from the Dearborn build that his car doesn't have a Thermactor, and the fact that it's a '65 puts it build date before the Feb. 14th change. MPC happens to list that combination as a Green marking, too.
Our philosophical difference aside, how can we help this person get his question answered? What methods can they use to bring out any remnants of paint markings on their existing springs? How do they go about looking for existing evidence? What has the rest of the Concours community seen in regard to this particular application, or front springs in general. And please 66GTCoupe let us know the rest of your options so we can try to get you the best information we can......