You can go to your local parts store and get any standard 180 thermostat. I haven't been following the thread, but here is what I would do: I don't know if the foam is an indicator of anything. Is the gauge accurate? Use a handheld food thermometer to directly check the coolant in the radiator. Losing coolant does point to head gasket leak. If you suspect a headgasket leak, drain enough coolant to remove the thermostat. Refill with coolant to the top of the thermostat housing. Remove belt, start engine, and check for air bubbles. If you have overheated the engine you may have a warped head/ leaking gasket. There is also an exhaust sensor that can detect exhaust gases in the coolant. Finally, some will argue that removing the thermostat caused the overheating. There has been much discussion on this board about this issue. It has been my experience that removing the thermostat only results in a cold engine.

Jason