Typically, although a far better car, like the Chevette all Kadett models have been the butt of jokes in Europe, particularly for being very common (the quintessential middle-class car in Germany and the Netherlands), very prone to rust and very easy to steal. While essentially good cars, and always praised as such by contemporary press, these gave Opel its commoner reputation it is still struggling to shake off.
The decklid badge says it's an automatic, but there's a four-speed manual inside. Was it a decklid or transmission swap? Either way, these cars were very, very cheap; the MSRP on a 1967 Kadett two-door sedan was $1,657 (about $12,500 in 2018 dollars), which compared favorably to the $1,639 Volkswagen Beetle that year. The Kadett had 54 hp to the Beetle's 53 (and weighed 93 fewer pounds than the Volks, to boot), so it was a bit quicker. On top of that, it had a heater that worked, plus a design dated a lot later than the late 1930s. Of course, most American car buyers looking for something economical preferred stripped-down versions of "traditional" American cars, e.g., the Chevy II ($2,090), the AMC Rambler American 220 ($2,073) the Ford Falcon ($2,118), or the Plymouth Valiant ($2,017). The Corvair two-door was $2,128 that year, too, and let's not forget the $1,790 Toyota Corona sedan.
The GSi's engine mapping had been carried out by Opel tuning specialists Irmscher. A model with the 82 PS (60 kW) 1.4 L multi point fuel injected engine, which was otherwise mechanically identical to the GSi, also became available as the Nova SRi in the United Kingdom. In January 1988, a turbocharged version of the Isuzu diesel engine was introduced, with power increased to 67 PS (49 kW).