The GTX was based on the Belvedere, and was differentiated by a blacked out grille and special rear fascia, fiberglass simulated hood scoops with optional racing stripes, a chrome "pop-open" fuel filler cap, and a tachometer mounted on the center console.

[2] Standard was Plymouth's 440 cu in (7.2 L) V8 engine called the "Super Commando 440" rated at 375 hp (280 kW).

The high performance 440 was standard in the GTX as was the TorqueFlite automatic transmission, while it was an extra cost option in the Plymouth Road Runner.

All featured dual horizontal "racing stripes" on the lower sides ending with a GTX emblem ahead of the rear wheel openings.

The GTX was positioned to be an upscale model of the Road Runner by adding elements of luxury to performance.

Stylists made the lines smoother, and a "power bulge" hood was introduced, as well as non-functional rear-brake air scoops.

The only other performance luxury model in Plymouth's lineup was the full-size Sport Fury GT, built on the C-Body platform.

The B-body was redesigned for 1971 and featured rounded "fuselage" styling with a raked windshield, hidden cowl, and a loop-type front bumper around a deeply inset grille and headlights.