Yes, there is a molded seal you need to get. By luck that is the only seal in the whole car that survives pretty well the years, and you should be able to get it at a P&P.
Your only other option is the Stealership...

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Aquilae non capunt muscas! (Eagles don't hunt flies!)


1979 300SD Black/Black MBtex239000mi
1983 300TD euro-NA. White/Olive Cloth-MBtex 201000mi. Fleet car of the USA embassy in Morocco
1983 240D Labrador Blue/Blue MBtex 161000mi