Two in One
A listing on Auction123 features a 1969 Ford Mustang Boss 429, one of the rarest high-performance variants of the first-generation Mustang. But what makes this example even more intriguing is that it comes with an extra “sister” Boss 429 engine – a valuable spare that can be rebuilt or just be sold.
Produced only for 1969 and 1970, the Mustang Boss 429 was created to house Ford’s 7.0-liter (429 cu in) big-block V8, a larger and more powerful engine than the one used in the Boss 302. The massive 429 was engineered as a homologation motor to help Ford remain competitive in NASCAR and challenge Chrysler’s 426 Hemi.
Backed by Proven Pedigree
This was critical during a period when Richard Petty – who would later become a seven-time NASCAR champion – briefly joined Ford in 1969, then returned to Plymouth the following year, where he drove the iconic #43 Petty Blue Superbird.
Because of its racing purpose, the Boss 429 power plant received extensive engineering upgrades. It featured a semi-hemispherical combustion chamber to improve airflow and maintain power at higher RPM, along with forged steel connecting rods and a forged steel crankshaft for exceptional durability under sustained high-load conditions.
This particular car’s engine is claimed to make 600 horsepower, roughly 225 hp more than the factory rating. Power is sent to the rear wheels through a four-speed manual gearbox. Other notable equipment includes its Royal Maroon exterior, vinyl high-back bucket seats, an AM radio, power steering, power front disc brakes, and a competition suspension.
The sister engine, meanwhile, is fully complete and has been disassembled for inspection. This allows prospective buyers to examine its NASCAR-homologated internal components closely and verify its authenticity.
A Heavy Hit to the Wallet
Despite the car’s high-performance nature, the seller says it has been garage-kept, well-maintained, and used as a show car and magazine feature. The pony car has 52,000 miles on the odometer, and the current owner has driven it for fewer than 200 miles. Further validating its authenticity and provenance are a build sheet, Mustang Club of America judging certificates, and a Marti Report.
The asking price is a staggering $410,000, but that’s expected for a five-decade-old muscle car limited to a little over 1,350 units. Interestingly, it even surpasses the price of Ford’s modern, race-ready Mustang, the 815-hp Mustang GTD, which launched at around $325,000.
