[aggie91]

Thanks for the input 88Ironduke.

I figured out the temp sensor wiring issue that I was thinking thru. After further investigation of the 1990 vehicle wiring diagrams (found on this site BTW), I did some parts searching. Turns out that GM put temp sensors/senders in the engine for a few years. The one that I first purchased was the one wired with a yellow and black wire in a 2 pole connector. Those wires go to the ECM on the 1990 engine. There is another temp sensor for the gauges, it is hooked up with a single dark green wire.

So a bit of searching on Rock Auto, turns up the part number for the sensor I need, TU66. So off to Auto Zone I go last night to return the one I do not need and get this one. they had it in stock and it was $3 less than the one I returned..

So, looks like I have all the items I need to complete my LS swap with the 1990 instrument cluster in my 1985 GMC C15.