[RCW]

From your description I do not think the sensor you have on the universal gauge will work. The bulb has to be fully immersed in the coolant stream and not block the passage. Extending it out will make it inaccurate as the coolant will not circulate correctly around the bulb.

I would replace the OEM sensor if it is defective and wire the light so it works, then pick up one of the hose kits and install the mechanical gauge in the radiator hose that takes the water from the engine to the radiator.

The issue with these engines is that the water at the OEM temperature sensor head can overheat and the radiator (radiator hose to radiator) can remain cool if the thermostat malfunctions or they get an air lock from low coolant. So, the OEM sensor is really needed.

I have used some electric water temperature gauge sensors on the Mule and installed an electric gauge as their sensors are much smaller and will fit in the OEM hole. The ones I used were from Dakota Digital and ISSPRO. Both run around $200.