I am trying to track down the correct fuel line/hose for my 1985 300D-Turbo. I received hose 107 476 24 26 which seems too big and after research seems to be used for the fuel tank vent line. I also received hose 107 476 37 26 which is has too small of an interior diameter to fit the metal lines.

Any advice on correct part number and/or correct ID & OD would be appreciated.

Fuel line for precisely where on the vehicle?

Don’t know about part number, but for primary (in-line) filter hose, the correct ID is 7mm. Bought a meter from belmetric yesterday.
This also works for one of the rear fuel lines and ditto for return if you’re not running the cigar line.

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1981 240D 4sp manual. Ivory White.

These would be the main rubber fuel lines, not the cloth covered return lines or clear plastic lines.