In the Pantheon of American muscle cars, the Pontiac GTO Judge and Plymouth Superbird rank among the most famous and powerful cars on the scene. Ford’s answer, the Boss 429 Mustang, didn’t get as much love or respect initially, as its 375 horsepower rating fell short of the 425 horsepower offered by both the Hemi 426 and GM’s venerable 427 motor, but as Jay Leno notes in this episode of Leno’s Garage, the Ford 429 was underrated and misunderstood from the very beginning.

This pristine 1969 Boss 429 Mustang was restored by Marcus Anghel of Anghel Restorations back to original showroom condition, right on down to the power-inhibiting smog pump that came with most Holley-powered muscle cars. But as Jay notes in the episode, the 429 engine had a sort of “semi-Hemi” combustion chamber setup, and though not a true hemispherical shape, it allowed the motor to make substantially more horsepower than its 375 rating would lead you to believe.

The reason, as Anghel notes, is because the Boss 429 engine was originally destined not for the Mustang, but the full-size Ford Galaxie, with the purpose of entering it into NASCAR. At the behest of GM turncoat Bunkie Knudsen, however, the Boss 429 was shoehorned into the longer and wider 1969 Mustang instead. But even though the pony car had grown significantly since its 1964 launch, Ford had to make a number of changes to fit the extra wide motor.

The biggest change was moving the shock towers out further in the engine bay to allow the wider motor to fit, but Ford also had to add a competition heavy-duty suspension package to distribute the extra weight. This included bigger sway bars front and back, not that it necessarily did much to improve the heavy Mustang’s handling. But the Boss wasn’t built for road racing, it was built for high-speed oval tracks and drag racing, and the first thing many owners did was chuck the GM-made smog pump as soon as they left the dealer lot.

That makes this period-correct restoration all the better, as do the rear drum brakes and engine oil cooler that was deemed necessary due to the 3.91 rear end gears. Leno and Anghel cover even more ground with their Boss 429 overview before hitting the road, and if you invest the full 20 minutes then you’re bound to come away knowing something about this big-block Boss that you didn’t know before.