Only 2 of these race monsters were made by the Opel tuning brand Steinmetz. They had a 6 litre V8 with 510 bhp.

After a few races in the Interserie 1974 (Good Year Pokal, 300 km Nürburgring 1974 von Peter Hoffmann) it disappeared from the scene and was exhibited in a showroom of an Opel-dealer for a short time. The whereabouts are unknown and mysterious, and it goes the rumour, that it was stored away and finally canibalized in a backyard, some parts of it still around in historic Opel-scene..

More pics in comments!