If my memory serves me right, the W126 models were introduced in the USA in 1980 as 1981 models, so there should not be an U.S. 1980 380SE.
The W126 line was introduced in the 1979 Frankfort autoshow, and began selling that same year in Europe.
Due to emission regulations and safety standards, the euro W126 and the American W126 were VERY different cars. The power output of the Euro model was 218 h.p., the American version had only 155 h.p. The bumpers, lights, and equipment fitted to the car were very different too.
If your car manual is in German, and is a 1980 380SE, it should be a grey market car. For parts and reference I will consult an specialist, as they may differ from model to the other. Although most body parts should be the same between a 1984 380SE U.S. version and a 1980 Euro version.
CL 500, 1998
S 500 L, 1998
E 320 T, 1995