The Plymouth GTX was introduced as the Belvedere GTX in 1967 by the Plymouth division to be a "gentleman's" muscle car.
It's most notable appearance in modern popular culture is in the television series Angel, in which the title character drove a black 1967 model.
It was to be an exceptional blend of style and performance. What differentiated it from a normal Belvedere was its special grille and rear fascia, shared with the Satellite, as well as mock hood scoops, chrome "pit stop" fuel filler cap and optional racing stripes. For the performance aspect of the vehicle, a heavy duty suspension system was made standard. Standard too was Plymouth's 440 cu in (7.2 L) V8 called the "Super Commando 440". The engine was rated at 375 hp (280 kW). Buyers in 1967 could pay an extra US$546 and replace the 440 with Chrysler's 426 cu in (7.0 L) Hemi. The 426 was nicknamed the "Elephant."
In 1968, after one year of production, the GTX was given a completely new look. A new hour glass body replaced the more box like body of 1967. The Road Runner was introduced by Plymouth as a performance version of the Satellite. There were major changes made in the design of all the Plymouth B-bodies. The Road Runner's base engine was the new 383 cu in (6.3 L) "Super Commando" V8 (renamed the "Road Runner 383"), while the high performance 440 was still standard in the GTX. The TorqueFlite automatic transmission was standard on the GTX, with it being a US$206 option in the Road Runner. The GTX was still based on the Satellite and was offered in two models, the 2-door convertible and the 2-door hardtop. The Road Runner was based on the Belvedere, and had less insulation and comfort items(padding, vinyl roof, trim), which reduced weight, helped produce better track times, and kept it in the low price field.
In 1969, the GTX's sales were hurt when the Road Runner was also offered in a convertible body style. The GTX received minor cosmetic changes, as well as the introduction of the optional Air Grabber hood (standard on Hemi-engined models), which made the hood scoops functional. The standard 440 V8 was still rated at 375 hp (280 kW). The 69 GTX was the last year that the convertible model was available on the GTX (VIN RS27). Chrysler Corporation only made 701 GTX convertibles in 1969. Of those, eleven were equipped with the 426 Hemi; four 4-speeds and seven TorqueFlite automatics.
The 1969 GTX also had standard black lower body side paint, replacing the dual, horizontal "racing" stripe on the lower sides of the 1968 model.
The 1970 GTX received a major redesign but sales still suffered. Stylists made the lines smoother, and a "power bulge" hood was introduced, as well as non-functional rear brake air scoops. The convertible model was dropped in 1970. The Air Grabber hood was brought back, but instead of having two narrow openings running length-wise as in 1969, it had one opening scoop located on the power bulge. The GTX was available with the standard 440 4 barrel, as well as the 440+6 barrel (three two barrel carburetors) and the 426 Hemi. The 440+6 could compete closely with the Hemi, up to highway speeds. In keeping with the GTX marketing strategy, the 1970 model included many standard features. The only other Plymouth luxury/performance model was the full-size Sport Fury GT, built on the C-Body platform. The GT was added to the lineup in 1970. The GT received nowhere near the recognition of the GTX, even though they shared many performance features. The Sport Fury GT was the full-size member of The Rapid Transit System. The Sport Fury GT was often viewed as more of a mature gentleman's performance luxury car.
Though completely redesigned for 1971, this was the final year for the GTX as a stand-alone model with only a manual transmission. Engine choices were 440 four-barrel, 440 with three two-barrels (Six Barrel), and 426 Hemi. Emission restrictions such as lower compression ratios and faster-acting choke operation lowered the base 440 output by 5 hp (3.7 kW), to 370 hp (280 kW). The 440 Six Barrel was down to 385 hp (287 kW), but the Hemi was still rated at 425 hp (317 kW). Due partly to rising insurance rates on muscle cars, sales were low. There were less than 3000 units produced in '71. For 1972 through 1974 the GTX became an option package on the Road Runner.