Ford Mustang 289 HiPo Convertible
The first actual muscle Mustang was made from 1965 to 1967 and was called the 289 HiPo or the K-Code Mustang. The 289 HiPo was the 271 hp V8 with improvements over the standard engine. It was available in all three body styles as a rare option (via YouTube).
For 1967, its final year, Ford produced only 50 convertibles with 289 HiPo engines. Most were equipped with manual transmissions, but 16 had automatic transmissions.