Steve especially,

Your test verified that coolant is circulating, your new fan switch works, 
and that your temperature gauge seems OK.  However, in an earlier post, you 
mentioned a running temperature of 160 degrees F.  That's too cool.  In 
fact, that is why I rambled on before about either an engine thermostat 
(not fan thermostat) problem, or, since you have a transplant, an error in 
the plumbing of the heater and coolant hoses.  I believe that you still 
have a problem.

Greg especially,

The temperature gauge reports the engine temperature.  As long as the water 
in the circuit is below the thermostat temperature, the engine runs at its 
usual 190 degrees F.  However, at a prolonged idle, the whole cooling 
circuit just keeps getting hotter because there is no cool water available 
from the radiator part of the circuit.  No airflow, no cool.  Eventually, 
when the whole system gets to 200+ degrees F, the fan thermostat on the 
radiator turns on and hopefully prevents any further increase in 
temperature.  However, after a few degrees cooling, the fan shuts off 
because the radiator temperature has fallen below the fan thermostat's off 
temperature, and the cycle starts over.  Thus, the way to bring the engine 
back down to normal is to turn it off, or to drive.

That's the design.

Mike