Tramp, that symptom of repeated spiking temperature then dropping seems exactly like mine before I added the external bypass to the water pump. The stat opens then allows a batch of cold water to enter the motor then it closes and repeats. When it closes without the bypass, hot spots develop before the stat opens again causing the temp gage to show the spike of temperature. You have to have an external bypass if the passenger side cylinder head does not have it built in. If your water pump was rotating the wrong direction I don't think the temperature would drop back to 180 when it over heats.
Mark
