[1930-Pickup]

There are places that specialize in this type is gauge repair.
I haven't used one in many years though, so I cant recommend one.

If your gauge has a long tube with a bulb at the end (I think so), its filled with ether gas.
As the temp goes up, so does the pressure of the gas.
So in reality, these temp gauges are actually specialized pressure gauges.

The only failure mode I've ever seen on these systems is when a leak develops and the gas leaks out, which makes the gauge read at its lowest setting.
It odd to hear that yours is stuck at 160, which makes me think it has a stuck gear in the gauge head.

Good luck
.