What "makes" a 66 Barracuda a Formula S ??

My 66 has all but the 4 barrel. But nothing on the car suggests a s model except the rear springs the rear itself 10-inch brakes all the way around. Heavy duty sway bar heavy duty torsion bars. The steel wheels are 13 x 7 so what does that make it? to me it is a great handling model of a fast back cool looker that makes me wish it was 1966 again. Its fast enough to satisfy my need for speed and a real classic that I love. It may not take any ribbons at the car shows but it gets lots of lookers wherever I take it. It has stolen my heart since the day I bought it. It gets more love than my wife and that all I have to say about that.