Updated

Talk about a markup.

A prototype of the 200 mph 2013 Ford Mustang Shelby GT500 sold at the Barrett-Jackson auction in Scottsdale this past weekend for $300,000.

Used to develop the upcoming muscle car’s 650 hp supercharged 5.8-liter V8, the mule was originally built in 2007 and modified with the new motor to put it through a full slate of endurance testing, including a 24-hour run at Sebring International Raceway in Florida.

Designed in-house by Ford’s SVT performance division, the automaker consulted on the car with racing legend Carroll Shelby, who reportedly took it out for a few laps of his own.

Read: $2.65 million Tucker leads parade of six-figure cars at Barrett-Jackson auction

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Sold in as-is condition, including some of the vinyl camouflage cladding worn on its redesigned rear bumper to thwart spy photographers, the GT500 is unfortunately not street-legal, so it’ll have to live out its years on the track or in a garage.

The 2013 GT500 goes on sale later this year with an electronically adjustable suspension to go with its new engine, purportedly the most powerful production V8 in the world. Pricing has not been announced, and the car it replaces lists for $50,000, but that doesn’t mean the bidder overpaid for the prototype.

All proceeds from the sale were donated to the Juvenile Diabetes Research Foundation.

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