In a Civic I used to own, my temp gauge would be normal and then all of a sudden it would just jump from the normal range to the max range of the needle... in that particular case it was just a band temp gauge and replacing the gauge fixed the problem. So I agree- that swapping out the cluster or at least just the temp gauge portion is a good thing to do if you've already done a bunch of other work.
Or you can just take it to a dealer pay the 100 bucks for the diagnosis - they can read the engine temp... while the car is running.... That's a safer bet than really letting your car overheat repeatedly.