Steve,

My cooling fan only comes on with the AC or if left at idle for 10 minutes 
or so.  Any driving creates enough air movement.

Have you checked to see if the engine thermostat is present and working 
properly?  The coolant is supposed to circulate only in the engine and 
heater circuit until the thermostat opens.  Only after that point should 
the radiator become a factor.  Which brings up another question.  Even with 
a good thermostat, if the engine was mis-plumbed, and the heater circuit 
connected to the radiator, the engine might not get up to proper 
temperature since the heater circuit is not controlled by the thermostat.

Mike  '84GL