When Pontiac introduced the GTO in 1964, other manufacturers said Me, too! and built models to compete against the Goat. However, it took three model years for Plymouth to respond with a model that would compete head-to-head with the GTO.
But when Plymouth introduced the 1967 GTX, it more than competed with the GTO it practically trounced it. Heres the story how Plymouth saved the best for last.
When relating the history of the GTX, you cant do it without revisiting how the GTO was created and the performance market at the time: In 1962, GM had over 50% market penetration. Legend has it they pulled out of racing in 1963 as one way to keep the Feds from accusing them of operating as a monopoly. This was especially bad news for Pontiac, whose success relied on the credo, You cant sell an old mans car to a young man, but you can sell a young mans car to an old man. In response, Pontiac decided to concentrate on street performance.
As the brand was about to introduce a redesigned and enlarged Tempest for 1964 following the lead of the mid-sized Ford Fairlane the model was ripe for a performance variant. However, politics at GM also led to a rule limiting the engine size for its new mid-sized cars to 330 cid. In Pontiacs case, that meant the most powerful motor available was the 326 HO rated at 280 horsepower, which was a fine motor but not up to the task of waging battle against 427 Galaxies or even 421 HO Catalinas.
The answer, to Pontiacs engineers and managers, was to create an optional package not a model that that took advantage of a loophole in the rules that allowed a bigger engine. With the GTO and its 389 a marketing and sales success, other manufacturers scrambled to offer their own GTO.
Meanwhile, back at Highland Park, the Chrysler Corporation was still reeling from a few years of bizarre Virgil Exner styling and a miscalculated downsizing of its bread and butter Plymouths and Dodges. Chrysler had the performance options for a screamer on the drag strip (426 Max Wedge and, come mid-year, the Race HEMI), but not much else for the street other than the brand-new 365-horsepower 426-S. It was more powerful than the GTOs Tri-Power 389, but no one was buying these cars, and the 383/330 wasnt competitive enough.
For 1965, the GTO packages second model year, Plymouth reconfigured its B-body line for the new mid-sized car class. The new model line started with the Belvedere I, then Belvedere II and topping with the Satellite, but Plymouth didnt have a dedicated performance model to compete with the GTO. Like before, these Plymouths could be optioned out like before with the Commando 383 and 426 V-8s but they were not giving Plymouth any street cred.
Things changed slightly for 1966 with the advent of the Street HEMI, but the HEMI was expensive and complicated for the average enthusiast. Plus, the models Belvedere and Satellite simply didnt have the cachet of GTO, and the market was demanding cars that had the image of performance. Pontiac was selling 96,000+ GTOs, Chevrolet sold over 72,000 SS 396s, and there were more than 37,000 Ford Fairlane GTs running around Every Town, USA, which were sales that could have been Plymouths but 10,000 383 and 1500 HEMI Plymouths werent making a dent. It was clear that Plymouth still needed an image car.