7T1vette

Certainly adding an A/C condenser in front of the radiator would increase coolant temps somewhat. Even with the A/C OFF, the airflow will be diminished a bit and the temps will go up a few degrees. With the A/C ON, it could increase 10-20*F.

P.S. Changing the thermostat will not achieve any drop in coolant temps; doing so will lengthen the time it takes to reach 'operating' temps...but not change what they are. To lower temps, you will need to improve airflow through your radiator set up and/or increase capacity of the radiator.

Apocolips

Could changing the clutch to a heavy duty type help keep the temps down a tad? I'm not sure what engine size the existing clutch came from. There were a lot of salvage yard parts used to put the car back together. It is entirely possible that the clutch came off a 305CI.

noonie

Yes it will add heat and in some cases cause the temp to increase. And the parallel flow will add slightly more than the original.
The temperature and amount of ambient air are the biggest factors in heat rejection and you are raising the air temperature available to the radiator.

Hayden makes almost all the replacement clutches, they also have heavy duty and severe duty. I would get one from a 75 or 77 w/ a/c. Most parts store have them.
Clutches do loose performance over time.

The way they are tested on Bimmers is to roll up a newspaper and carefully press it against the running fan on the driver's side (not jam into it), a good heated clutch will be hard to stop or slow and a poor one will slow down or stop easily.
Of course if you want to try this method, be very carefull at your own risk.