I agree on the stock gauges behind inaccurate. Also, I'd like to meet whomever designed the wiring and circuitry for the gauges. Almost every 5.0 I've owned has the same problem of the temp gauge going up 10-20 degrees when you put the lights on. On my current one it goes from about the middle of m-a to almost 1/2 way on the gauge.
Regarding the stock vs 180 stat. I dont think there is any harm in running a 180 stat, but engines tend to operate more efficiently when hotter - obviously to a point- better mpg, oil flow, etc. My point was too often people think swapping to a lower temp stat will solve some other cooling system issue such as overheating etc..