A mark of General Motors' confidence in their plans for the small car sector, and something that the Opel Kadett and the Vauxhall Viva had in common, was that the manufacturer built for each new model a completely new car plant in a region characterized by relatively high unemployment and the availability of a skilled workforce, but with no strong tradition of volume auto-making. The Vauxhall Viva was the first car built at Vauxhall's Ellesmere Port plant while the Kadett A was the first product of Opel's new purpose built Bochum plant. Ellesmere Port and Bochum would effectively become sister plants, producing subsequent generations of Kadett as well as their Vauxhall badged sisters (the Chevette and Astra) for the next fifty years.
The manufacturer now offered two versions of the Kadett, designated the "Kadett KJ38 and the "Kadett K38" the latter also being sold as the "Kadett Spezial". Mechanically and in terms of published performance there was little to differentiate the two, but the "Spezial" had a chrome stripe below the window line, and extra external body trim in other areas such as on the front grill. The interior of the "Spezial" was also better equipped. To the extent that the 300 Mark saving for buyers of the car reflected reduced production costs, the major difference was that the more basic "KJ38" lost the synchromous springing with which the car had been launched, and which continued to be fitted on the "Spezial". The base car instead reverted to traditional rigid axle based suspension similar to that fitted on the old Opel P4.
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).