I have a tank from a 116 300SD. I know the 116 tanks are a bit bigger than the 126 81-85 but not sure about the SDLs. If you find it will work and are interested pm me.

Good luck!

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2009 ML320 Bluetec
1985 300CD
1981 300TD

Past Mercedes
1979 300TD
1982 300TD
2000 E320 4Matic Wagon
1998 E430
1984 300SD
1980 300SD