Need help finding new temperature gauge

That's the whole problem.............the cluster depends on the dash --- to cluster mounting bolts, which is not all that dependable. That's why I suggest a separate pigtail

You can easily test the cluster / gauges out of the dash now that you have some test resistors

Clip your 1/2 scale (23--25 ohm) resistor to the sender stud on one of the gauges, and clip the other end of that resistor to ground.

Hook the cluster ground to battery neg.

Hook the proper pin of the harness connector to the battery hot, and watch the gauge.