Well I finished the replacement of the wiring harness on my daughter's '84 240.
It was a fairly hard job since there were several other things to work on while I had the intake manifold pulled back. I did the following:

1. Removed and tested the engine temperature sensor. It tended to run a bit high on resistance vs temperature but not horrible.
2. Removed and cleaned the oil separator (yuck!) should have had a new one. The O-ring under the separator was flat and hard. I think that was the source of the oil on the bottom the oil pan. Replaced O-ring.
3. Replaced both heater hoses just because they were handy to get at.
4. Cleaned the left side of the engine of all that oil mess.
5. Removed, diassembled and cleaned the throttle body and idle air control motor. New gaskets on throttle body and intake manifold.
6. Replaced harness, cleaning all connectors with DeOxit while so doing. The old harness was toast and the jacket so hard I had to cut the harness in three pieces to get it out.
7. Used Gunk to clean bottom of engine when all was done. Now I'll be able to see if and where the oil leaks, if any.

This all took about a day and a half, I'm old and slow.

Next I'll replace the splash pan when the new one arrives from IPD.

I bought the wiring harness from Dave Barton and I sure do recommend him to everyone, as others have also done. The harness he sent was in great shape, pliable, clean, good connectors too. I replaced the LH fuse holder but that's all it needed. Dave also included full notes on the wiring diagram, color code at each connector, etc. A very thorough man!

Altogether a satisfying job to have done but I'm not anxious to do another one soon. Also the idle air control in now functioning.

If anyone plans to do this, be sure to bag and label parts, have some spray cleaner such as brake cleaner, use DeOxit on connectors, maybe take some pictures, and don't be in a hurry.