I can't see a leaking head gasket/bad head causing this thing to get that hot, that quick, without mixing in with the oil, and/or blowing the coolant out of the rad...that just don't make any sense in my pea-sized brain.
I know mine will start the temp gauge swingin to the "HOT" side anytime I'm just sitting still, in traffic, especially after coming off the hi-way. That leads me to believe, as others have pointed out, that there's really not a lot of coolant flow at idle on these things. I shudder to think what it would do in a parade on a hot, Texas summer day! :heat: :heat:
A restriction on the suction side would certainly explain the low flow...if it cain't get in, it cain't go out!