Thing is, it is easy to build a car from parts, since just about every part ever made by Cox was also available separately. While I suspected that the Ford GT could have briefly been issued with the later chassis and motor (TTX150), I doubted it because Cox had built quite a stockpile of it. By 1966, they must have run out of them and still hade demand, so must have issued the TTX150 version (briefly) at that time. But I had yet not seen an intact kit, and until I did, I was a bit skeptical.
The Cheetah was never issued with the TTX100 motor, but it is easy to make one up: use an earlier Ford GT chassis and motor, and fit the shorter drop arm of the Cheetah and the older guide on it and voila.
But show me a kit, sealed in its original box, and that's another story!
Interestingly the last production of the Cheetah used the same chassis but cast in aluminum instead of magnesium, and I have seen some truly rare ones, sealed, with a Mabuchi FT16D with the oval can hole in lieu of the Cox NASCAR motor made in Hong Kong.
The same mystery surrounds the 1/24-scale version of the Ford GT: it appears that early issues were fitted with the TTX100 motor, just like the Ferrari and BRM F1 cars, but no kit has yet surfaced to prove it. Circumstantial evidence however, exists: the "second" issue clearly points out to an update, now with a new chassis and the larger TTX200 motor, a Mabuchi FT36, endbell-side driven. The "third" and most common issue is of course the TTX250, yet with another new chassis and a can-side driven Mabuchi FT36D. Do you still follow?
Below is the "second" issue, with a sticker claiming "now with a TTX200 motor". If we take "now" as an update, the only possible earlier issue is fitted as the other cars issued at the same time, with a TTX100 (Mabuchi FT16) motor.
Little mysteries of collecting...