The “Boss” badge first appeared on the Mustang in 1969. That’s when Ford introduced two homologation specials wearing this name: the Boss 302 and the Boss 429.

The 302 version was developed specifically for SCCA Trans-Am racing. The production version got a unique stripe package and a 302-cubic-inch (4.9-liter) V8 rated at 290 horsepower, which turned it into a competitor for the Chevrolet Camaro Z/28.

The Boss 429, on the other hand was used as a mule for the company’s then-new 429-cubic-inch (7.0-liter) V8. The NASCAR-spec mill was eventually raced in the Torino Talladega, but it was homologated in the Ford Mustang. The Boss 429 was the most potent first-gen Mustang ever at 375 horsepower (alongside the Cobra Jet).

Both cars were produced in limited quantities in 1969 but returned for a second model year in 1970. The Boss 302 sold 8,948 units, while the Boss 429 moved 1,358 examples. Both were discontinued at the end of the 1970 model year.

Ford actually had plans to keep the Boss 302 in production for 1971. The company even went as far as to build a prototype and show it to the public. However, the project was scrapped just a few weeks after the vehicle’s debut.

But even though the 302 and 429 were canceled, that wasn’t the end of the line for the “Boss” badge. Ford slapped it on a Mach 1-like version powered by a beefed-up 351-cubic-inch (5.8-liter) Cleveland V8. And just like its homologation-spec predecessors, it was short-lived and became a rare gem.

The Boss 351 found only 1,806 customers in its sole year in showrooms, which makes it the scarcest iteration of the 1971 Mustang. The pony had a slow year in 1971, but Ford still managed to move 149,678 units. The Boss 351 made out only 1.2% of the total production. The dark green example you see here is one of those cars.

While not quite as rare as the Boss 429, this muscle car has it all. It’s highly original, it still sports the factory-correct color, and it rocks a numbers-matching drivetrain under the hood. It’s unclear whether the paint is original or an older restoration, but the two-tone brown interior hasn’t been altered. And it looks tremendous for a car that’s 52 years old as of 2023.

The engine looks like it may have gotten a few upgrades, but that’s not surprising for a car that’s been on the road for so many decades. Most parts are period-correct anyway and do not alter the V8’s numbers-matching status.

Speaking of which, this is not a run-of-the-mill 351 V8. This beefed-up, four-barrel version came with 330 horsepower on tap, 90 more than the H-code variant. It also generates 45 horses over the M-code Cleveland. All told, it was the second most potent Mustang at the time.