Did your truck slip through customs without ever being federalized. There must be some importation documents. If you can get a letter from the EPA it would help. Is the PA title in your name? California DMV only smogs vehicles from 1995 and later. They still have to be compliant even if they don't get tested. Maybe its 1979 for gassers and 1995 for diesels.
There is or was a company that imported a lot of GWagons. They could be of help. I wish I could remember the name.
Keep trying and be sure to be in touch with the main DMV office in Sacramento. The person who got my car through was from that office. If you have the PA title in your name it should work. You might need some documents from PA DMV. Find out the state where it was first imported. If you can get an EPA pass that should get you in write them a letter. It may take a while. Be the squeaky wheel, annoy the hell out of them on the phone at the Sac office. It took me forever. One person from the DMV told me I would never be able to register my car here. Well she was wrong.

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Chris
84 280sl
82 300d euro