Introduced for the 1967 model year as an upscale-trimmed version of the Belvedere, the Plymouth GTX was marketed as the “gentleman’s muscle car.” But even though it had a slightly fancier interior and came with more comfort features than the average intermediate, there was nothing gentle about the GTX performance-wise.
Because while the Belveere was available with a long list of V8 engines that also included the entry-level 273-cubic-inch (4.5-liter) and the low-power 318-cubic-inch (5.2-liter) mills, the GTX was all about thumping big-block power. Specifically, it came standard with the massive 440-cubic-inch (7.2-liter) RB, while the only option available was the mighty 426-cubic-inch (7.0-liter) HEMI.
The four-barrel 440 delivered a solid 375 horsepower, enough to send the hardtop down the quarter-mile in about 14 seconds. The six-pack version of the same unit generated 390 horsepower, while the range-topping 426 HEMI came with 425 horses on tap. The latter turned the GTX into a 13-second sleeper at the drag strip.
But while 425 horsepower was a big deal back in the late 1960s, it’s far from extreme nowadays. Especially after Dodge introduced the insane Challenger SRT Demon 170, which lays a whopping 1,025 horsepower on the pavement right off the showroom floor. So it’s not surprising that some Mopar enthusiasts are dropping beefed-up powerplants in their freshly restored muscle cars.
It’s not very common to see a GTX with a nasty surprise under the hood, but this 1970 example in Sassy Grass green is proof that this type of modding goes beyond the more common Road Runners and Barracudas. And as a fan of the GTX, I think that’s downright awesome.
Being a sucker for Chrysler’s “high impact” color palette and especially Sassy Grass, I wouldn’t really care what’s under the hood. Because this Mopar looks fantastic inside and out. Not only is the green finish perfect and true to the original hue, but the interior also sports a cool combo of green and black leather and vinyl highlighted by wood grain on the dashboard, the center console, and the steering wheel. I don’t think Plymouth offered this combo back in the day, but I don’t care, to be honest, because it looks stunning.
But I can’t ignore what lurks under the black-striped, air-grabber hood. Because the owner ditched whatever this GTX got from the factory for a 500-cubic-inch (8.2-liter) V8. There’s no info as to what exactly it is, but I’m guessing it’s a stroked 440-cubic-inch RB. It kinda looks like a 440 and no one would be so crazy to ruin a rare HEMI car for such a mod. How powerful is it? Well, that’s yet another piece of info we don’t get, but this mill definitely cranks out more than 500 horsepower. In fact, I wouldn’t be surprised if it sent more than 600 horses to the rear wheels.
And speaking of which, this GTX rides on the fattest rear tires I’ve seen in a very long time. And I bet it uses them to pull some amazingly fast quarter-mile times. Anyway, while we can’t see it do that in the video below, we can hear that massive V8 rumble while idling. And, boy, does it sound delicious, especially when the owner bypasses the mufflers at the 1:37-minute mark. But make sure you watch the entire thing because there’s a bit of revving toward the end.