What’s the exact process to identify a real 66 Formula S Barracuda?

It looked like this when I took it apart for paint in 1981. My wife and I actually had dinner tonight with a sister of the guy I bought it from. Lifelong friends are great. I loved the car, but it wasn't what I really wanted at the time I sold it. I wanted to build a big block Dart and wasn't about to swap a big block into the GTS convertible, plus our second kid was on the way and we needed something "practical" to go along with the GTS.
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