A quick way to test the gauge would be a one-burner propane camp stove sitting on the intake manifold, a pan of water, and submerge the sending bulb in the hot water. The bulb doesn't care if it's actually in the engine or not, and you wouldn't even have to remove it from the truck.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!