'61 temperature gauge

[Klas]

Just finishing wife's '61 fleetside short box, 283 cu. in. powerglyde. During a shake down cruise, the original temperature gauge would go almost to the hot side.
Using a digital temperature gun, the thermostat housing read 180 degrees.
Because the speedometer starting going crazy, I decided to replace it and the temp and fuel gauge as long as I had to take the cluster back out.
Sourced and installed Counterpart gauges and speedometer.
Before reinstalling the cluster back in the dash, I tested the lights etc. Letting the truck run outside in 85+ degree heat with the air conditioning on, the needle on the temp gauge would only come up to the cold line.
Checked the temperature again at the thermostat housing, it reads 187 degrees.
I have a new wiring harness, 180 degree thermostat, 01513321 temp sender and no sealant on the sender into the intake.
The gauge is wired correctly (12v to ignition and other side to the sender as marked on the back of the gauge).
Am I missing something or just have a bad (new) temperature gauge?