1970 Ford Mustang Boss 429 Fastback

The Boss 429, sometimes referred to as the "Boss 9" by Blue Oval enthusiasts, is arguably one of the rarest and most valued muscle cars from the era. In total there were 857 original ’69 Mustang Boss 429s, then only 499 Boss 429s for the 1970 model year. The origin of the Boss 429 was a result of Ford’s desire to compete in NASCAR. Ford was seeking to develop a Hemi engine that could take on the Mopar Hemi boys, the 426 Hemi Charger Daytona and the Plymouth Superbirds, the monsters Ford had to slay to achieve its desire to rule the track. NASCAR required that at least 500 cars be fitted with the competition motor and sold to the general public.

The Boss 429 engine featured aluminum cylinder heads, which had a modified Hemi-type combustion chamber Ford called "crescent." The Boss 429 engine used a single 735 CFM Holley 4-barrel carburetor mounted on an aluminum intake manifold. All these cars had the Hurst Competition shifter and 4-speed manual transmissions, and the Boss was rated very conservatively at 375 HP, though actual output was believed to be well over 500 HP.

Mustangs were simply too small to accept the massive Boss 429 engine, so Ford hired Kar Kraft of Brighton, Michigan, to modify existing 428 Cobra Jet and Super Cobra Jet Mach 1 Mustangs. Modifications included widening the shock towers and extending out the inner fenders. The mounts for the front suspension were chopped and displaced to create room for the block and exhaust manifolds. The battery was repositioned to the trunk, and a stiff 3/4-inch sway bar was added to the rear end to improve handling since the car was now nose-heavy. It was also equipped with a 3.91-ratio rear axle with a Traction-Lok limited-slip differential. In addition, a hole was cut in the hood and a manually controlled hood scoop was added. Other features included a front spoiler and color-keyed dual racing mirrors.

In short, all Boss Mustangs are simply big-block power with few options. These very special cars were given NASCAR identification with a "KK" number that was placed on the driver's side door. The second model year, 1970, came with very minor changes and production was drastically cut back. Changes included the mechanical lifter camshaft and an improved dual exhaust system, though rated power output stayed the same. The biggest change was the five new exterior colors: Grabber Blue, Grabber Orange, Grabber Green, Pastel Blue and Calypso Coral.

This Boss was built on September 9, 1969, at Dearborn and then delivered new to Larson Ford Sales Inc. in Murray, Utah. Opening the hood with the fully functional air-gulping hood scoop, which were all painted Matte Black in ‘70 regardless of the color of the car, reveals the monster Boss 429 engine. The engine bay is correctly detailed throughout and is complete with all the production chalk marks, tags and decals. The matching-numbers Boss 429 engine is connected to its matching-numbers RUG 4-speed close-ratio manual transmission with the mandatory Hurst Competition shifter. It also came factory equipped with a V-code 3.91-ratio rear axle with a Traction-Lok limited-slip differential.

This Boss, representing the rarest production year of the Boss, has received a beautiful rotisserie restoration. It looks striking in the rare factory Code J Grabber Blue, which has excellent depth and beauty. The interior features the white Clarion knit/Corinthian vinyl Hi-Back bucket seats. Even the restoration of the undercarriage reflects a high level of the quality restoration and the detail taken to have this Boss present as seen here. A Marti Report also confirms the other features including the Drag Pack, Convenience Group, clock, rim-blow steering wheel, console, power steering, power front disc brakes, AM radio, Decor Group, Deluxe seatbelts with warning light, Competition Suspension and the tachometer and trip odometer. Documentation includes an Elite Marti Report and a copy of the original Ford invoice.

Only 499 Boss 429s were built for 1970, making these legendary cars a rare sight. With its attractive color combination and beautiful restoration, this example will certainly turn some heads. Being of this high quality and well documented, this Boss 429 is an investment-grade collector car and perfect for the astute Ford enthusiast.