Some interesting side notes on the Factory Experimental classes with NHRA. It was introduced in 1962 at the Winternationals in Pomona, CA. None of the cars entered in A/FX in '62 were factory built cars, all were built (or converted) by their owners. In 1963, only the Chevy Z-11 and the Pontiac Swiss Cheese cars could be said to have been factory built cars, and at the time, they were built to compete in S/S, not in F/X. NHRA disallowed them for S/S so if they ran at NHRA events, they ran as F/X cars. Ford didn't build a factory F/X car until 1965, with the Mustangs. They did offer "pieces" that could be used to build an F/X car, primarily light weight body parts, beginning in late 1962. If I remember, the Mercury Comet F/X car was introduced in '64, and Pontiac introduced the 421 Tempest as an F/X car in '63. And as far as Dodge and Plymouth, I don't think they ever offered a factory built F/X car. They tried with the AWB cars but they were disallowed by NHRA before they ever ran.
There has been plenty of misinformation over the years about the difference between a "legal" F/X car and a Match Race car. Basically, there were no rules for a Match Race car, whereas the F/X cars could not deviate very much for rules for the S/S class. Pulling the front bumper, using a tube front axle, running with non factory light weight parts, cars like that were never allowed to run in the F/X class. F/X was a great class but Match Racing was where it was at. Remember, F/X only ran at NHRA National Events, and I think there was only two or three National Events in the beginning of F/X. Plus, there was no money in it. The money was in Match Racing.
http://georgeklass.net/fx.html