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

That's like my very 1st '66, which I still have. It has all the options, but, not a FS. It's also a heater delete car. Very unusual.

It's why I love Mopars while my Dad has always been a Ford fan. It seems that no two mopars were built alike. I've seen 66s with 64/65 parts on them. Now learning that you could buy a FS with everything but the badge. They are all so unique!