It probably was. It had a V8 in it and I think it was a copy of the chevy small block.
In Europe, Opel is the GM brand and they use some GM engines. My wife wanted an Opel. I forget the model but it was one of their top of the line models with all the bells and whistles so I got one for her. When I opened the hood I was astonished to fine a Chevy "Stovebolt" straight 6 in it. But not just any "Stovebolt". Split manifold, dual exhaust, 4bbl carb....it was the old "Corvette" 6, and it was a screamer. I could get in the left lane on the autoban and run with the BMW's and all the other big boys with it.