This is most likley going to start some kind of agrument, but here goes.
Do you have a Marti report. I ask because, I did not know somethings before I bought my car. That a marti report revealed. I also have a F-code. My car had an option called the Sports Appearance Group, (SAG). It is a rare, early 1969 option that included racing mirrors, hood scoop, possible slats, spoiler front and back, and most of the mach 1 stylings, but different stripes. This was an early sales promotion by Ford. Sorta like the Cali Specials, Twister specials. They only made just over 5,700 of these. In the future who knows if these will be of any collector value. In comparison. about 78,000 mach 1's were made in 1969, and only something like 56,000 Sports roofs that were not mach 1's. These are not exact numbers. The point is that your car and mine is technicaly rarer than a mach 1. The nice thing about an F-code is that you can do whatever you want to them. If you modify it, no one minds. You could hurt the value of a R-code car if you changed the color, rims, stance, etc. You could potentialy increase the value of your F-code with the correct mod's. I see it all the time on B/J auctions, where a resto-mod, modified, or clone car can sell for thousands of dollars above what the same car would have sold for, if it was stock. Sometimes they sell for more than a R-code, if done right.
Anyway.
Why get hung up on a decor option. Make it a clone if you want too. In the future any mustang is going to command good money, because they are only getting more scarce. I think, in the distant future, the cars options are going to become less of a factor reguarding prices. People will just want one and not care about it being a different color, or having a different engine than what was original.
If you just have to have a peice of paper that says it's real mach 1, then get one. The previous owner put mach 1 stripes on my car. It is very rare for someone to ask me if it's a real mach 1., and most would'nt know the difference anyway. Do what makes you happy, But dont forget how lucky you are to have one.
Even if it isnt a real mach 1.