[Alleggerita]

Here's an entry at the Nurburgring in 1976 as #78 - car entered by Hähn - though car apparently did not arrive/run - no picture but I would say that it certainly would have been wide body as in the model.

GP Nürburgring 1976 - Photo Gallery - Racing Sports Cars

 

[Alleggerita]

Not sure if you are looking for the actual car or you plan to build a replica - how true to the original is it going to be? More likely than not the Jägermeister/Maschke car was either owned by Hähn in Mannheim or was an ex-Hähn car. At least two of the Hähn GTA's that ran as GTA juniors in the early to mid 70's were actually 1600 cars that were converted to 1300 spec. The Maschke car likely sported a narrow angle head, possibly 4-valve. It would probably be worthwhile to talk to Helmut Hähn.