The 1965 Shelby Mustang GT350R Prototype driven by legendary Brummie racing driver Ken Miles is now the most expensive Mustang in existence, selling for a whopping $3,850,000US ($5.85m NZ) at Mecum Auction’s Sale at Indianapolis on July 17th. This means the original racing Shelby Mustang just pipped the $3.4 million US record set by the famous highland green Mustang GT390 …