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

My 64 Barracuda was later put together with Formula S parts and was was a joy to drive anywhere and everywhere. My 66 Formula S did not have the racing stripes and had 10 in drums all around with 7 1/4 rear with sure grip. Both were great cars. I guess if you are a numbers matching guy, it makes a difference money wise. I never was. I just lucked into my 66 Formula S. My cousin wanted it and his father would not let him have it. So I bought it.