The Plymouth GTX made its debut in 1967, one year before the Road Runner became Plymouth's most popular model. It was originally designed as a "gentleman's muscle car", offering an alternative to the Pontiac GTO, Ford Fairlane GT and such (and later Plymouth's own Road Runner).
- 1967 - GTX's premiere year, and based on the Plymouth Satellite (itself an upmarket Belvedere), and available as a hardtop coupe or convertible. The 375 hp 440 cid V8 was standard, the 425 hp 426 cid Hemi being optional. The 440 and Hemi were both available with a 4-speed or Torqueflite automatic, either on the column or console. 125 GTXs had Hemis, 14 of them convertibles - and a little known fact is in 1967 if you wanted a Hemi in your Plymouth, the GTX was your only choice - it was no longer available on the base Belvedere model as in 1966. The 1967 GTX was a one-year-only bodystyle, as the mid-size B-body line was being redesigned for 1968.
- 1968 - Plymouth actually had 2 muscle cars based on the same car, with the less-expensive Road Runner making its debut this year. While the Road Runner was basically little more than a base-model Belvedere with a big block engine and a heavy duty suspension, the GTX was based on the upmarket Satellite and offered nicer surroundings and features than the Road Runner did, again keeping with its "gentleman's muscle car" image. GTXs had unique tailights that ran all the way across the rear end, something the Road Runner didn't have. GTX sales paled in comparison to the Road Runner, though - the Road Runner cleared over 50,000 sales this year - the GTX didn't even come close to that amount. Engine choices remained the same as in 1967, with the 440 standard and the Hemi optional with the same horsepower ratings (the 440 4 bbl wasn't available in the Road Runner).
- 1969 - Not much changed this year, the biggest visual difference being a new grille and restyled taillights that were still unique to the GTX. The 440+6 (or Six-Pack) wasn't offered on the GTX, guess it didn't fit in with it's "gentleman's musclecar image" (although the Hemi supposedly did, go figure). The GTX continued to remain in the Road Runner's sales shadow more this year as it was continuing to rake in all the glory... but some appreciated the GTX's quiet, understated and perhaps more mature nature.
- 1970 - Minor body restyle this year, but interior and chassis dimensions remained the same as in 1969. The 440 continued to be the base powerplant with the Hemi remaining optional. The Road Runner continued to be the darling of the bang-for-the-buck crowd, but the GTX carried on in its own right, remaining a viable alternative by those perhaps turned off by the Road Runner's "bad boy" reputation.