Carroll Shelby built only 562 examples of the original 1965 GT350, a Mustang so stripped-down and race-focused it barely resembled the more comfortable 1966 version that followed it. Hertz alone would go on to order more GT350s for its rental fleet than Shelby sold at retail. Read on to find out how one VIN code stamped with the letter ‘R’ can separate a genuine early Shelby from a look-alike.