Stunning just doesn’t do it for this Mustang.

This 1970 Ford Mustang Boss 429 Fastback goes under the hammer in Sydney on Sunday when it is expected to fetch upwards of $400,000.

Regarded by many enthusiasts as the ultimate Pony Car, it’s finished in Grabber Blue with White Knit Vinyl Décor upholstery.

More importantly, it’s factory-fitted with all the sought-after Boss 429 features, including a manual gearbox, the Drag Pack, power front disc brakes and competition suspension.

This car arrived in Australia in 1996.

Its engine has been rebuilt with a new longer stroke crank, new pistons and rods, while the induction system was upgraded with a Holman & Moody-type setup with twin carbs.

Dyno-tested to confirm 595.9 horsepower at 6000rpm, the Mustang now shows just 33,360 miles on the clock.

Shannons believes it to be one of the finest 1970 Boss 429s to come on the market and expect it to sell in the $340,000-$380,000 range.

In muscle car terms, Boss models built in 1969-1970 have grown in stature to become some of the most desirable Pony cars of all and the Boss 429 is widely regarded as the biggest, baddest Mustang ever sold to the public.

The Boss 429 was essentially a street machine used to homologate the big-block engine for NASCAR while Ford used the smaller-engined Boss 302 to homologate the Mustang for the SCCA’s Trans-Am road racing series.

It’s the brainchild of Ford president Bunkie Knudsen, who came up with the idea of dropping the 385-series 429-cid V8 into the Mustang sportsroof, teaming up with Larry Shinoda to create the ‘Boss’ package.

Unlike the regular production Boss 302, the Boss 429 Mustang was hand-built at the Kar Kraft facility in Brighton, Michigan and each car was assigned an individual KK number between KK1201 and KK2558.

Production commenced in January 1969 and 859 units were completed that model year, with a further 500 examples completed as revised 1970 cars.

As part of the process the Mustang’s engine compartment was extensively modified, with relocated shock towers and revised suspension, a three-quarter inch rear sway bar, boot-mounted battery and reinforced HP429 engine block with four bolt mains, forged steel crank and con-rods, Hemi-type alloy cylinder heads, a 735cfm carburettor, hydraulic lifter camshaft on 1969 models and an engine oil cooler.

The transmission was a four-speed close ratio manual and 3.91 rear axle with Traction Lok.

The striking Boss package consisted of a front spoiler, manually controlled bonnet scoop, chrome Magnum 500 wheels with Goodyear Polyglas GT tyres and a Deluxe Décor interior featuring an 8000 rpm tacho and AM radio as standard.

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Riley

Chris Riley has been a journalist for almost 40 years. He has spent half of his career as a writer, editor and production editor in newspapers, the rest of the time driving and writing about cars both in print and online. His love affair with cars began as a teenager with the purchase of an old VW Beetle, followed by another Beetle and a string of other cars on which he has wasted too much time and money. A self-confessed geek, he’s not afraid to ask the hard questions - at the risk of sounding silly.