It seems that a bad wire harness might not manifest itself in failures if not disturbed, but flexing it as much as you would have to R&R the head could have killed it.

Fuel smell is something else, have you checked the fuel pressure regulator vacuum hose for fuel?

If you're near SW Michigan, I might be willing to trade an almost-new engine harness for an engine swap (M104 out, OM603.960 in, I have the diesel engine and parts).

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Gone to the dark side

- Jeff