Photo: YouTube/John Clay Wolfe
By the late 1960s, Ford was on a high-performance killing spree, producing ever more powerful (and larger) engines to counter the nefarious terror of the Chrysler 426 Hemi. Hot on the heels of the 428 Cobra Jet and its “Super” sibling, launched in 1967, the next step was the legendary 429, introduced for the 1968 model year. The bigger Cobra Jets were great engines, but they still weren’t enough. In 1969, Ford went all the way and dropped the biggest hammer it would ever produce during its golden era: the Boss 429.
The rationale behind the groundbreaking 429 big-block was to have it ready for NASCAR, where the Hemi was racking up wins and championships with virtually no challenge. In 1969, the Charger Daytona became famous. FoMoCo bosses had learned the vital lesson they had taught Chrysler in 1965 when the Race Hemi was banned after Ford complained that the hemispherical-headed engine had no street-legal counterpart.
Mother Mopar released the street-legal Hemi in 1966, blowing everyone else away. Ford couldn't fall into its own trap, so the big 429 was produced in sufficient numbers for the general public to get the nod from NASCAR executives. The Boss 429 was born, one of the Blue Oval's most coveted powerplants.
A very limited production run of 857 units met homologation requirements (the governing body of stock racing required a minimum of 500 cars to be sold to everyday civilians). They are much rarer than a Hemi vehicle and just as desirable since the Boss Nine was only available for two years (1969 and 1970).
Photo: YouTube/John Clay Wolfe
The Big Boss also had a little brother, the Little Boss, the 302. It was built for the same purpose as the Big Block: homologation, but for SCCA racing (in other words, Trans Am). However, despite being available for the same amount of time, it achieved much higher production numbers. While the Boss 429 only collected 1,368 units in the two years it was built, the Boss 302 collected 8,641 units.
Ford realized the potential of the name and didn't simply pull the plug on the Boss moniker after 1970, although both the 429 and 302 would eventually leave the scene. In 1971, the third (and least famous) member of the Boss trifecta was launched: the Boss 351. In keeping with the tradition of putting the engine's displacement in the name, the last Boss relied on a 351 Cleveland V8 introduced in late 1969 for the 1970 model year.
In its special Boss application, the 351 developed 330 horsepower, thanks to its 11.7:1 compression ratio, a configuration reserved exclusively for the 1971 Boss, although the engine was used in every other Mustang model in the lineup, including the Mach 1. The latter model was the longest-running model in this Boss-Mach series, lasting from 1969 to 1978 (with two further iterations between 2003-2004 and 2021-2023).
Photo: YouTube/John Clay Wolfe
Finding any one of the three would be considered a jackpot win by any collector, but stumbling upon all three under the same barn roof is definitely the Holy Grail. Well, every now and then, miracles do happen, and John Clay Wolfe from Give me the VIN will attest to that with his latest barn find. A '69 Boss 429, a '71 Boss 351, and a '71 Mach 1, kept hidden from humanity for a good two decades or more somewhere in Glen Rose, Texas, have emerged with great restoration potential.
The condition of the cars is encouraging, to say the least: the Red Mach 1 starts right up and even the power windows work. The yellow Boss 351 needs some work (the carburetor and valvetrain are covered in rags, but otherwise the Mustang looks solid and clean). The Royal Maroon Boss 429 is the crown jewel by a considerable margin and sports some rare original equipment not commonly found on other examples available on the market.
The air cleaner snorkel and smog kit (pump and canister) were generously discarded from the 429-cubic-inch V8’s high-performance engine to allow it to express its full potential. The seven-liter engine was officially rated at 375 hp (375 PS) and 450 lb-ft (380 PS, 610 Nm), but its true potential was well above those numbers. This particular example sports an original 28,527 miles (45,910 km) on its odometer, and its former owner had it since the early 1980s.
Photo: YouTube/John Clay Wolfe
In second place in sales was the Boss 351. With 1,806 units, it was the rarest series available in the Mustang lineup in 1971, and was accompanied by a mandatory wide-ratio four-speed transmission and a 3.91-inch Traction-Lok rear differential.
For special track or drag strip applications, the 351 Cleveland could be equipped with oil cooling hardware and special valves (titanium for the intakes, or special steel alloy for the exhausts). Interestingly, the 1971 Boss Mustang was the only model that had no direct connection to racing, having been built specifically as a street model (albeit a high-performance one).
Finally, the 1971 Mach 1 is another gem that stands tall among the legendary Ford products of all time: the 429 Cobra Jet decals on the side of the dual-scoop hood need little introduction. Seven liters of high performance in a Mach 1 was not a common sight that year.
Photo: YouTube/John Clay Wolfe
Of the 151,000 Mustangs assembled, 36,500 bore the Mach 1 badge, but only 815 of those were ordered with the big-block V8. To put things in perspective, its rarity surpasses that of both the same-year Boss 351 and the 1969 Boss 429.
Like all barn finds, these cars need some restoration to get back to peak condition, but these aren’t just any old Ford Mustangs—they’re special models that typically pass from hand to hand between people who have both the means and the will to care for them.
