Where is the needle supposed to be on a 59 temperature gauge at full normal operating temperature? Should it be dead center or around 3/4 towards Hot? Also, are there different sending units that measure differently or are all single terminal temp senders interchangeable?

I ask because I installed an NOS temp gauge (because it has a good non-rusty face) and it shows hotter than my old gauge did. I'm running a 180 degree thermostat. Doesn't seem to overheat, but the NOS gauge just shows the needle farther over than the old gauge.