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

this formula s thing is an interesting dilemma...A barracuda basically came with whatever the buyer and salesperson sat down and decided it would unless there was a order restriction that was not able to be changed. I have a 1965 barracuda with a 273 commando, 4 bbl, heavy suspension, sway bar, 4 gear, factory tach etc that is a non formula s car but rather a fender tag 5 option..."performance package barracuda"