By the late-1970s, Ford's Mustang was struggling to keep up with the competition, having become bloated and underpowered. The third-gen Mustang would be built on what is now known as the Fox-Body platform, bringing America's favorite car back into a sporty arena with a boxy exterior that would come to typify cars of the 1980s. An often-overlooked sibling of the Ford Fox-Body Mustang is the Mercury Capri. And now, a Mercury Capri prototype car that was built with input from McLaren Engines Inc and a Cosworth inline-four under the hood has been listed on the auction website Bring a Trailer with only 500 miles on the clock.

Coulda Been A Contender

Mercury Capri Cosworth McLaren Prototype 4
via Bring a Trailer

Compared to the production Mercury Capri, which was basically a boring version of the Mustang, this car shows where Ford could have gone with Fox-Body cars to make them even sportier. The custom prototype bodywork was built by Ron Fournier and features awesome fender flares, side intakes, a front splitter, and revised rear quarter windows.

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Under The Hood

Mercury Capri Cosworth McLaren Prototype 3
via Bring a Trailer

The exterior hides a fun driveline under the skin, highlighted by a Cosworth-built BDA inline-four with double overhead camshafts, a dry-sump oiling system, and dual Weber carburetors. The setup routes power to the rear wheels through a five-speed manual gearbox from ZF and a nine-inch rear end equipped with a locking differential.

RELATED: These Forgotten Mustang Prototypes Almost Made Production

Interior Touches

Mercury Capri Cosworth McLaren Prototype 2
via Bring a Trailer

Perhaps the best part of the interior is the aggressively bolstered seats, which are Recaro Model C units matched by a sporty Raia steering wheel and a custom-built aluminum dash. The car features 15-inch, three-piece BBS wheels that hide front disc brakes and rear drums — the latter being perhaps the most disappointing aspect of what is otherwise an awesome overall creation that should have been brought to the market exactly as it sits today. Bidding has already reached five figures with six days remaining in the auction.

Sources: bringatrailer.com and cjponyparts.com.

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