Going to change my thermostat today, my temp needle seems to be moving up a little higher then usual though it's not over heating , radiator, heater core are new, just serviced the transmission with filter/gasket kit and fluid and changed the oil and filter. The 302EFI long block and temp gauge sending unit were new in 2008 with low miles, I don't DD a lot anymore but I reused the T-stat so it maybe around 6-7 years old time to be replaced.
Recently I put on a new radiator cap mfg by Murray's from O'Reillys but the quality seemed poor and I noticed that it had backed of a half turn by itself under pressure so I went back the one I had on there which is in good shape but several years old so I may change that as well just to be sure.
I think when it backed off by itself it may have sucked in air so I'll burp the system when I get it all back together today...
I'm going with a 195* Mr. Gasket which has a god reputation, I couldn't get a 195* from Motorcraft....IDK...
Good Luck ~ :thumbup