Single wire water temperature sensor?
You could get a 3 wire sensor made for a '98, and pull off of the 3rd wire. (if you also got a connector for it.) Not sure what the signal range is exactly, but it's the same one that directly drives the gauge on a '98 f-body. The other 2 wires go to the pcm, same as the 99+.
Or you can get one from Autometer, I'm not sure if it comes with the right adapter, probably not. But it is one wire, and would have to go in the passenger side head. Easiest way to get to it is to remove the header and put it in from under the car.
