The first generation Opel GT (1968-1973) debuted as a styling exercise in 1965 at the Paris and Frankfurt motor shows. The production vehicle used mechanical components from the contemporary Opel Kadett B and two-door hard top bodywork by French contractor Brissonneau & Lotz. The styling of the GT was often cited as similar to the 1968 Chevrolet Corvette which went on sale in September 1967. The Opel GT was equipped with a base 1.1 L OHV straight-4 engine, which produced 67 hp (SAE) at 6,000 rpm. However, most buyers chose an optional 1.9 L camshaft in head engine, which produced 102 hp (SAE) at 5200 to 5400 rpm. Some of the early 1968 models also came with a slightly higher compression "H" code cylinder head. In 1971, due to emissions regulations, Opel reduced the compression ratio of the 1.9 L engine used in the US and output fell to 83 hp (SAE). There was also a GT/J model, which was a less expensive version of the 1900-engined GT which was sold only in Europe. Standard transmission was a manual four-speed. A three-speed automatic was available with the 1.9 L engine. The model run of the Opel GT was from 1968 to 1973.