Carroll Shelby had a good relationship with Ford at Dearborn after the AC Cobra, Shelby Daytona Coupe and his work on the Ford GT40 project, so Ford turned to Shelby to make a hot version of the Ford Mustang. Shelby first had to agree with the American SCCA what was needed to make the Mustang eligible A stock Ford Mustang 2+2 Coupe was given a tuned 4,727cc engine with 4-barrel carburettor, hot camshaft, revised rear axle, shock absorbers and 306 bhp. 35 300lb lighter racing versions ('GT-350R') was also produced as well as 562 street versions for 1965. The 1966 model was mildly restyled. A special black GT-350H model was produced (936 out of 2,380 sold) for hire by Hertz until they discovered that clients were taking the car racing. But Shelby came up with the GT-500 model for 1967 with a 428-cu.in. V8 under the bonnet and 3,225 were sold in 1967. For 1968 the Shelby came as either the 302 or 350 supercharged engine or the 428, but Ford was now making them at its own plant and they were more mainstream; 4,450 produced in 1968. Shelby ended the agreement in 1969.