I agree, parting it out wouldn't just seem right for a nice example like this one. Give yourself a beer (or two) and a few hours of free time and that harness is done. I've done a few M119 harnesses. Simple plug-n-play job. Plus, I think the 400E's have really dwindled in numbers sadly as I hardly ever see one anymore.

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Only diesels in this driveway.
2005 E320 CDI 243k Black/Black
2008 Chevy 3500HD Duramax 340k
2004 Chevy 2500HD Duramax 220k