Written by independent automotive journalist Steve Statham

Content Provided by Barrett-Jackson

When it comes to American muscle cars, there are two distinct breeds. There are those that were built up from simple workaday coupes and sedans, and then there are those that were built to race and were detuned just enough to operate on the street.

The Boss 429 Mustang is definitely one of the latter.

Ford created a full stable of performance Mustangs in the 1960s, but the Bosses were the ultimate thoroughbreds. The Boss 302 was built to excel in Trans-Am road racing, while its big brother was created to be the production home for Ford’s new NASCAR racing engine, the Boss 429.

The Boss ’9 V8 looked every bit the part of a race engine. Its massive magnesium valve covers topped cavernous cylinder heads with semi-hemispherical combustion chambers that Ford called a “crescent” design. There were numerous differences between the NASCAR engine and the street version, but the production engine still boasted a spec sheet worthy of a racing motor. The bottom end had thick main webs, four-bolt nodular iron main bearing caps, and a forged, cross-drilled crankshaft. The cylinder heads had huge ports and intake valves, and used O-rings between the heads and block instead of gaskets. Like any proper racing engine, the Boss 429 had an oil cooler to keep temps under control.

Ford installed a streetable cam in the production engines, along with a 735 cfm Holley carburetor mounted on an aluminum intake manifold and fed by a functional hood scoop. The engine was rated at 375hp and 450 ft/lbs of torque, though few believed those conservative numbers.

The Boss 429 engine was so physically large that Ford set up a special assembly line for the cars at Kar Kraft in Brighton, Michigan. To fit the engine in a Mustang, Kar Kraft reengineered and widened the shock towers and installed a thinner brake booster to allow clearance. The battery was relocated to the trunk to free up additional room.

To back up the large, powerful engine, Boss 429s were fitted with a Traction Lok differential and close-ratio 4-speed. The suspension was beefed up with thick front and rear sway bars.

Ford built 857 Boss 429 Mustangs in 1969. This Royal Maroon 1969 Ford Mustang Boss 429 (Lot #1360) offered at No Reserve at Barrett-Jackson’s 2016 Scottsdale Auction is a prime example of the breed. It was recently painted and freshened, and still sports an amazing number of its original parts.

The car has racked up only 19,500 miles in its life and was stored with its engine removed for decades. It has all its original sheet metal and has never had any rust. It retains its matching-numbers engine, 4-speed transmission and rear end, along with correct carburetor, fuel pump and water pump. Even the power cable running between the engine and the trunk-mounted battery is original.

That originality extends to the interior, which only needed the carpets and seat covers replaced during the freshening. The door panels are original and as-new. The seatbelts were restored by Python. On the exterior, purists will appreciate such as the Ford script headlamps and the fact that the lower valance has never been drilled for a front spoiler.

All the original suspension pieces were reused, except for the shocks and tires. The undercarriage is correct in every detail, with stamps, paint marks and part numbers throughout that reflect just what you’d have found if you’d had this car up on a service lift in 1969.

To call something “boss” in the 1960s was teen slang for things that were exceedingly cool, and the Boss 429 Mustang more than lived up to that. The “Factory Special” market is always hot at Barrett-Jackson. For a reminder of why this BOSS ’9 Mustang is so special, check it out at Scottsdale