This is really a mod - sorta. When I did the open cooling thing, I installed a '92 up thermostat neck from the junkyard. I came with a sensor in it, I wired it into the original harness. It worked fine. No muss, no fuss. Fan kicks in right smartly, and if you want one that trips at a lower temp, they are discussed somewhere - I'm still looking for the post myself.
A Comanche overflow tank will barely fit between the air box and fender, the wiring loom is too bulky. I used longer screws with a 3/8 spacer between the tank and fender to leave room, and relocated the puel pump resistor further down the inner fender to prevent splicing up wires.
Now my engine runs a little too cool, I installed a three core, but it sure doesn't overheat either. I have Lebaron vents to make things even worse - that's the next mod!