John, you don't mention if the radiator cooling fan is coming on. If
things are getting that hot, you should hear the fan come on low
speed,then high. If you pull the radiator bleeder like Benny suggested
(simple things first like David Vickery suggested,) I bet you will not get
hot coolant. So, from how I read things here, unless your rad fan is out,
your thermostat is stuck closed. You can just go in and pull it out,
without putting another one in there, for the sake of troubleshooting,
replace the thermostat housing cap and do another test run. If the fans
come on and you are getting hot liquid to the rad, then presto! Damn, I
hope for your sake that this is it. Good luck. Miguel