The first evolution of the First Generation Ford Shelby Mustang was offered for the 1965 and 1966 model years. These high performance cars were built by Shelby American using a standard Mustang as a base. For the first evolution of the 1st Gen Shelby Mustang, the GT350, GT350H, and GT350R variants were offered, both of which were only available in a fastback body style. Power for these cars came from Ford's 'K-Code" 289 cubic inch 'HiPo' V8 engine (4.7L), which was modified to generate 306hp. The 1965-1966 Ford Shelby Mustang was replaced by the 1967-1968 Ford Shelby Mustang.