• Ford offered Boss 302 and 429 versions of Mustang from 1969 to 1970; the Boss 351 was built for 1971 only on a larger, restyled Mustang body
  • The original Boss 302 cars were designed to dominate SCCA Trans-Am racing with a high-revving small-block V8 and outstanding road-holding capability; Boss 429 cars were designed with acceleration in mind and built to satisfy NASCAR engine homologation requirements
  • All classic Boss models are coveted collectibles today thanks to outstanding performance and limited production numbers

Arriving in 1969, the first Mustang Boss was forged from a simple mandate by Ford management to the designers and engineers: Create a Mustang that would be unbeatable on SCCA race courses and local drag strips alike.

By then, Mustang sales success was assured thanks to its sporty nature. As a true high-performance icon, however, the car’s history had yet to be written. That changed when company leadership decided to pursue dominance in the popular SCCA Trans-Am road racing series. They chose to homologate their new NASCAR 429 engine using the Mustang, directing engineers to begin creating performance that would become legendary.

The result – Boss – spanned three engine configurations across two Mustang bodystyles, each of which remains a coveted classic among enthusiasts and collectors today.

1969-70 Boss 302
With styling tweaked by newly arrived Ford designer Larry Shinoda, the new-for-1969 Boss 302 sported front and rear spoilers, a blacked-out hood treatment, and racy side stripes for a look that screamed performance.

Under the bodywork, the Boss 302 didn’t disappoint. Its engine combined a four-bolt main Windsor small-block with reworked heads from the then-new 351 Cleveland engine. A forged steel crankshaft, connecting rods and pistons rounded out the reciprocating assembly. The result was a free-breathing, high-revving power plant making what Ford claimed was 290 gross horsepower – though actual output is estimated to be significantly higher.

Ford engineers also thoroughly massaged the Mustang’s suspension in an effort to meet then-boss Semon “Bunkie” Knudsen’s mandate to “build absolutely the best-handling street car available on the American market.” Stiffer springs and shocks, special sway-bar tuning, a stiffened chassis and wide tires led to the fastest Mustang ever to lap the Ford test track up to that point.

1969-70 Boss 302 specifications
Engine: 302-cubic-inch (5.0-liter) OHV V8
Horsepower/torque (advertised):
290 hp @ 5800 rpm/290 lb.-ft. @ 4300 rpm
Transmission: Four-speed manual
Production: 8,641

1969-70 Boss 429
While the Boss 302 was intended to be a perfectly balanced road race car, the Boss 429 had a decidedly different mission in life – uncompromised acceleration. Although the exterior appearance was similar to that of the Boss 302, the 429 engine under the hood was a heavily detuned version of a new Ford NASCAR racing power plant.

The choice of Mustang as the model used to meet the 429’s homologation requirements – rules dictating a certain number of a manufacturer’s stock car engines were actually sold in production vehicles – was considered unusual given that Torino was Ford’s NASCAR flagship at the time. Plus, the effort required to shoehorn the huge 429 between the narrow Mustang shock towers dictated that the cars were heavily modified under the skin – work farmed out to Ford vendor Kar Kraft. Much of the front suspension was re-engineered to make the transplant work, and the battery was relocated to the trunk to provide additional room.

Even with special chassis bracing and a unique rear sway bar, the “Boss Nine” was at its best when pointed in a straight line: With a few owner modifications to undo the factory detuning, the car could yield quarter-mile times in the low-12-second range. That performance, coupled with big-block appeal and low production numbers, has conspired to make the Boss 429 perhaps the peak of Mustang collectibility.

1969-70 Boss 429 specifications
Engine: 429-cubic-inch (7.0-liter) OHV V8
Horsepower/torque (advertised):
375 hp @ 5200 rpm/450 lb.-ft. @ 3400 rpm
Transmission: Four-speed manual
Production: 1,356

1971 Boss 351
Boss returned for one more year, this time wearing the new-for-1971 sheet metal marking a longer, lower and wider Mustang than ever before. Under the hood, changes were equally dramatic, with the company’s 351 Cleveland V8 supplying the basis for motivation, matched as always with a four-speed manual gearbox. But with Ford pulling out of all factory-sponsored motorsports after 1970, the Boss 351 was denied a key element cementing the status of its predecessors: the proof testing provided by an official racing program.

Still, the Boss 351 offered exciting performance and eye-catching looks aided by the 60-degree sloping fastback body and twin-scoop contrasting hood. Interiors also gained luxury options; coupled with the improved tractability of the 351 Cleveland engine, it was easier for prospective buyers to turn this final early Boss into a comfortable high-speed cruiser than was possible with the race-bred 302 and 429 iterations.

1971 Boss 351 specifications
Engine: 351-cubic-inch (5.8-liter) OHV V8
Horsepower/torque (advertised):
330 hp @ 5800 rpm/380 lb.-ft. @ 3400 rpm
Transmission: Four-speed manual
Production: 1,806


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