Photo: American Mustangs/YouTube

Ford already had three performance-oriented Mustangs in showrooms in late 1968. The GT was available with up to 325 horsepower, while Shelby offered the track-ready GT350 and the beefed-up GT500. Of course, we can’t forget the 428-cubic-inch (7.0-liter) Cobra Jet that joined the lineup mid-year.

In 1969, though, Ford rolled out three more cool rigs. The Mach 1 was available with almost any V8 engine, so it wasn’t exactly exclusive, but it had a unique appearance package and race-bred suspension. As for the Boss twins, both were developed for homologation purposes.

The Boss 302 enabled Ford to continue racing the Mustang in the ever-demanding SCCA Trans-Am series. A competitor for the Chevrolet Camaro Z/28, it featured a bespoke 302-cubic-inch (4.9-liter) V8 engine and, just like the Mach 1, unique visuals.

The Boss 429 wasn’t designed to go racing, but it brought the massive 429-cubic-inch (7.0-liter) V8 into showrooms. This move was necessary so that Ford could use the powerplant in NASCAR. And, of course, the 429 came with special features you couldn’t get on other Mustangs.

Finally, all these bundles worked great with the styling cues of the 1969 pony, arguably the best-looking first-generation Mustang model year in my book.

However, the 1968 model is nothing to sneeze at either. Sure, Ford didn’t offer as many performance-oriented rigs that year, and the car itself didn’t look as aggressive, but the fastback version is still a sight to behold. And it makes for a nice sleeper with the right powerplant under the hood.

The GT you see here may look like a run-of-the-mill Mustang at first glance. It’s finished in the ubiquitous Candyapple Red paint, and the thin black stripes are nothing special. But take a closer look, and you’ll notice the larger rear wheels wrapped in fat tires. Well, they’re not there just for show. All that rubber transfers a great deal of oomph to the ground.

It comes from a custom-built engine that is larger than anything you can find in a first-generation Mustang. I’m talking about a mill put together by Jon Kaase Racing Engines, which offers a wide range of Ford-based units, including FE and SOHC lumps. This one’s based on a Boss 429, but it’s been stroked to 572 cubic inches. That’s a whopping 9.4 liters.

According to our host, the engine was dynoed at 840 horsepower. It’s unclear how much actually reaches the wheels, but that’s enough oomph to put this old Mustang atop most modern muscle cars, regardless of the nameplate.

And besides being an asphalt-twisting rig, this fastback looks the part inside and out. The exterior is flawless, while the interior includes a few modern upgrades you’d expect to find in a street rod. The list includes custom gauges, a center stack control panel, a padded dash, and a roll cage.

Not surprisingly, the massive engine makes quite the racket while idling. And even though this Mustang is not a drag car, I bet it could give the Dodge Challenger Demon a run for its money down the quarter-mile. Hit the play button below for a detailed walkaround.