I have great memories of an old Opel we had decades ago. My bil put a racing motor in it and I had so much fun with it. I learned to drive a straight shift on Memorial Parkway. Guys would come in the other lane and I would leave them in the dust. Of course, I was a lot younger back then. I miss it. : )
My Step-dad had an Opel GT, red of course. The One that resembled a small Corvette. It was really fun to drive......................
I recall there were a couple of after market suppliers of hop-up parts for the Kadett. A buddy owned one of these “full race” Kadetts in Iowa City. It would turn 7,000 rpm and make a sound like a hoard of killer bees.