Originally Posted by RangerPilot
The two wire sensor is for the PCM signal of how warm the engine is. It doesn't effect the gauge.
The one wire sensor is the one you need, it should be located right about where the upper radiator hose meets the intake manifold. You say there is a plug in this place. As I said before, remove this plug, buy a sender, install it in that location, and hook the wire up. The wire should be right there, it has a "boot" at the end.
Oops, I misread the Julien's initial post. Zach is correct - you want the SINGLE WIRE SENSOR (BK/LB color wire) which is commonly called a "temperature sender" or "temperature sending switch". It's for the instrument cluster gauge.
Good catch Zach.