Looking at the NAPA part, I only see the one threaded sensor location which inserts the sensor into the coolant stream to the heater core. The second hole in the picture is a mounting hole, not a threaded location.
All of the OBDII 4 Liter XJs use the same water outlet. In the OBDII vehicles, the sensor feed a voltage to the PCM via a pair of wires. The sensor does not require grounding as it is a thermistor. As the temperature changes, the resistance in the sensor changes and so the voltage the PCM sees changes. The PCM uses a look up table to determine the coolant temperature which is reported as "ECT" on an OBDII scanner.
ODBII vehicles all share the same part number for the sensor be the engine a Diesel, the 2.5L or the 4.0L. Chrysler finally figured out that is was less expensive to have one sensor to do both functions. So, they use the same sensor to drive a gauge or the idiot light. Which is why it is possible to swap out the dash cluster from idiot lights to the full gauged cluster. No sensor changes required.
NAPA lists only one sensor for the '96 model year. They list the same part number for the '95 model year as well. Looks like the water outlets are the same for the H.O. engines as well.
So, perhaps a photo of your engine would have some value here...