I did a little research and it turns out that modern replacement fan clutches are set to engage at higher temps than the originals, so they can be used on a larger number of modern car application. You can adjust the thermostatic spring engagement temp lower if you move the outer spring starting point counterclockwise by a small amount. This thread deatils it:
http://www.forums.maxperformanceinc....=776003&page=2
The first photo is the spring in the original factory location. The center valve only moves about 45 degrees to engage the internal valve and lock the clutch. I tested the spring with a head gun and a infrared thermometer and you could see the spring lengthen and turn the inner valve as it got hot around 190 or so.
Second photo shows the spring moved CCW to the left of the retaining location. When heated with the heat gun, it engaged at around 160-170 degrees. You can't just leave the spring like this as it will not disengage the valve if it is not retained in both directions of travel.
I fashioned a retaining clip out of a wiring retainer bracket so it encompassed the circular mount area as well as inside the circle through the original slot. I then used JB Weld to keep it in place.
The last photo shows another person's similar clip but on a rectangular mounting location on a different clutch.
Now, as I wait for the JB Weld to fully cure, I guess I'll give Gramma's car a well deserved wash, claybar and wax since I can't remember the last time I cleaned the outside of this car.