’66 383 HOT/COLD sending unit location

I'm going to plumb in a water temp. gauge soon when I get the correct thermostat housing installed, and I've found a suitable place for the sending unit to go right underneath the AC Compressor. It currently has a "plug" in it. But I'm curious as to where the hot/cold light sending unit is - everyone says "the front of the engine" but I'm not seeing it. Is there another place it might be besides on the water pump housing?

TIA
Author: darth_linux