Originally a NASCAR homologation special, this Boss 429 now blends period-correct looks with staggering performance upgrades.
Factory Origins
The 1969 Ford Mustang Boss 429 was never intended as a typical muscle car. Built primarily to homologate Ford’s new 429-cubic-inch V8 for NASCAR, only about 850 examples were produced for that model year. Each was modified by Kar Kraft in Brighton, Michigan, since the standard Mustang engine bay couldn’t accommodate the oversized big-block. This particular car, finished on May 20, 1969, was assigned Kar Kraft number 1837 before being delivered to Phil Long Ford in Colorado Springs.
The NASCAR Connection
In the late 1960s, Ford was in direct competition with Chrysler’s 426 Hemi on the NASCAR circuit. To counter, engineers developed a semi-hemispherical big-block capable of sustaining 7,000 rpm. Homologation rules required at least 500 street cars, leading Ford to turn the Mustang fastback into a Trojan horse for its racing program. Kar Kraft’s modifications included widening shock towers, moving the battery to the trunk, and reworking front suspension geometry. Handling on the street was compromised, but the car’s purpose was singular: to put Ford’s new engine into NASCAR.
A Name with a Story
The “Boss” name was coined by designer Larry Shinoda, who jokingly referred to the secretive project as “the boss’s car” in reference to Bunkie Knudsen, Ford’s new president. The moniker stuck, first with the Boss 302 and then the Boss 429, cementing its place in Mustang lore.
Modern Heart, Classic Body
While originally equipped with Ford’s 429 semi-hemi, this car underwent a dramatic transformation in 2018. The factory motor was replaced with a Jon Kaase Racing Engines 598ci V8, built around a Ford Motorsport block. The naturally aspirated unit features a 15:1 compression ratio, a Get’M Garage 1,650-cfm carburetor, Hedman headers, and MSD 7AL ignition. On the dyno, it produced a staggering 1,062 horsepower and 817 lb-ft of torque, nearly triple the output of the factory-rated 375 hp.
Drivetrain and Performance Upgrades
Power is sent through a four-speed manual transmission, paired with a McLeod twin-disc clutch and a carbon-fiber driveshaft. At the rear sits a Traction-Lok differential with 4.11:1 gears and 35-spline axles. Calvert Racing springs and Mickey Thompson drag radials hint at the car’s quarter-mile intentions, while braking remains vintage in character with front discs and rear drums.
Exterior Details
Visually, the Boss retains its 1969 identity. Painted in Black Jade, it carries the correct Boss 429 badging, functional hood scoop, and rear window louvers. The car rides on 15-inch Magnum 500-style wheels, shod with Cooper tires up front and drag radials in the rear. Though heavily reworked mechanically, its period appearance remains intact.
Interior Mix of Old and New
Inside, the cabin keeps its original flavor with black vinyl bucket seats, a rear bench, and woodgrain appliqués on the dash, console, and door panels. A heater and AM/FM radio remain, but modern touches like an Auto Meter tachometer, auxiliary gauges, and a choke control bracket have been added. The odometer shows just over 62,000 miles, though only about 20 miles have been added by the current owner.
A Street-Legal Monster
Despite its drag-strip performance credentials, this Boss 429 is registered for the street in California, making it one of the most powerful road-legal Mustangs in the state.
At the time of this writing, the Bring A Trailer listing shows 2 days left of the auction, with the top bid sitting at $125,500. We'll keep an eye on the auction to see how it ends up!
