Just got a 2004 SRT-10 with a little over 43K miles. Only problem so far are the parking brake light is always on and the cruise control won't engage. I,m going to search for "normal" operating temperature when its only 107 degrees outside.
A big Kiwi welcome from NZ. I have some fond memories of AZ Park brake light usually a switch fault or adjustment. I would imagine temp gauge will read above 200 most times in summer. There are some other AZ people on here that will confirm. Hey you may even be able to catch up with them.
Welcome to RBC. The brake light might be the emergency brake switch going out I had the same problem until I swapped it out. The ABS ask Rotten Ronnie he knows more about our 10's internals.
In regard to the normal temp it depend on your locality and thermostat. My truck runs 210-220 but the big fan and radiator keeps it in check. These trucks matter of fact, all SRT's I have owned run hot.