Like I said, I ain't positive about this model vehicle, just been the case
in a few vehicles I've owned.  Call Napa and see what they offer. I bet napa
has an online catalog, or someone does. I just feel if the gauge is steady,
and records low on startup and gradually goes to 160, I doubt another gauge
will accomplish anything.

Just my cents, which don't add up to that much.

I would not replace the dash gauge. It won't make any difference. Had
the same problem on my 96. Took it to a cummins dealer. They put a
mechancal gauge on to check everything out. They ended up replacing the
therostate twice.  My 96 ALWAYS read about 160 or less....even when I
ordered  replacement thermostats from Cummins.  There were some
thereostats that would cause wide swings in temp when they would open
up. That was caused by the large cooling  capacity of the dodge
radiator. Cummins finally came out with a modified thermostat that
fixed that problem.

I say don't worry about it. I put 160k on my truck before I traded it
off and it was still going strong.

Ron