Of all the Mustangs in Ford's considerable stable of cars spanning an impressive 50 year run, perhaps none is more well known than the legendary BOSS 429. With only 1,359  examples produced for the 1969 and 1970 model years, the BOSS 429 is one of the rarest and most expensive Mustangs ever made. She was originally designed and built around the famous 429 BOSS, "Shotgun," or "Semi-Hemi" engine to satisfy NASCAR homologation rules. With a stated output of 375 hp in street trim, which independent experts state is over 100 hp below the true figure, she had the power and looks to turn anyone's head.

Up for sale today and ripped from the pages of Hemmings Motor News is a 1969 Ford Mustang BOSS 429, KK-NASCAR # 1881 with 20,562 miles on the odometer and a sale price of $310,000. So what made the BOSS 429 so great?

3 The 1969 Mustang Fastback Body Style

via Hemmings

With it's graceful lines, dual headlights up front, a wing out back, faux intakes on the rear haunches, and Magnum 500 wheels, the 1969 BOSS 429 certainly looks like she means business. This was a departure from the 1967 and 1968 body style made famous by Steve McQueen in the movie "Bullitt." The body carried over into the 1970 model year with little change except for the front and rear tallights. The current example is finished in Royal Maroon. Looks pretty good, doesn't she?

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2 The Interior

via Hemmings

The interior is a premium Mustang option with high-backed bucket seats, tasteful simulated woodgrain interior, fold down rear seats, a full console, and padded dash. The car was treated to a full restoration at the 17,000 mile mark and has won multiple trophies since that time.

1 The Engine, The Engine, The Engine!

via Hemmings

The famous BOSS 9 was developed out of the Ford 385-series engine family and took multiple wins down the quarter mile drag strip and around NASCAR ovals. She featured four bolt mains on the bottom end, a forged crank and connecting rods, aluminum cylinder heads, aluminum intake manifold, and a Holley carburetor. The engine was so big that the cars had to be shipped off to custom car fabricator, Kar Kraft, to modify the shock towers so the engine could fit under the hood.

As to whether or not it's worth $310,000, I'll let you be the judge. But with numbers diminishing, and a strong resale market, it seems like a good price for the condition it's in.

Sources: Hemmings Motor News

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