Does this rare Ford GT prototype have what it takes to bring in an eight figure sum at the RM Auctions? It's only 1 of 4 in the world and was used by Ford and Shelby as a testing platform for the Le Mans race cars.

The Shelby GT350R is one of the rarest and most valuable Shelby Mustangs on the planet, valued on average around $1 million. Just 36 of these cars were ever built, including two prototypes, and one of them is about to head to auction.

This weekend RM Auctions sold a Ford GT40 with links to Steve McQueen for a record $11 million. That is the most money ever paid for an American car at auction, though amazingly it wasn't the highest priced sale of the event.

With just an estimated 25 1965 Shelby GT350Rs left in the world, no wonder they are among the most valuable Mustangs ever. This weekend one of these uber-rare Mustangs sold for an incredible $990,000, just shy of the $1 million mark.