Summer Operating Temperature

Yesterday I changed the thermostat in my '91 5.0 lx from the stock 195* to a 180*. I live in Tucson, AZ and the high got to around 100* give or take and with 30-45mins of run time the car stayed around the R and M of NORMAL. I'm guessing that would be 200*-210* roughly. What my main question is, however, is this the correct operating temperature with those conditions listed? Am i still running too hot, or is it just from the outside temp that's causing it?

From what i heard the 180* t-stat doesn't open until about 200* anyways. So, would this be a normal summer operating temperature here in AZ?

Thanks in advance!

Fixed! I ran the car later with the rad cap off, to make sure all the air bubbles had a chance to get out, bleeding it thoroughly. The heater was on full blast for about 15 minutes during this too, since I've seen that helps. I noticed after starting the car that the coolant level was really low, so I filled it up to the rim while the car was on, put the rad cap back on and went for a test drive. She held up perfectly and stayed around 180* the whole drive.