Firenza's were sold in Canada, and were an updated Vauxhall Viva, completely different from the Opel Kadett. Ours were all 4 cylinders, and had horrendous reliability issues. In South Africa, 100 were converted to V8 power, all with Z/28 302 engines, just to make them legal for a local racing series. This would have been a handful on the street, but I would have loved to drive one! Some still survive in New Zealand, and here's a photo of a vintage racer.
Flickr photo