Just a question. Is the top of your engine higher than the top of your radiator?? If so the engine will get air locked. I'd check the thermostate and maybe flush the engine. Your not realy getting to hot but it is a situation that should be checked. How hot dose it get after you turn it off? You could run the engine with a hose in the radiator and the drain open and see how hot it gets. Over heating problems can be a pain but can be solved. When you changed the water pump you didn't perchance get one for a serpintine belt set up did you??? Sounds like a nice ride you'll get it figured out in time.