Can I be too cool?

[tucsonjwt]

I think you are correct. I just drove the truck about 15 miles, mostly highway, and the temp gauge is still sitting around 160-165. Since the original thermostat was definitely not opening (or not opening properly), I suppose I was running hot for a long time previously, but the gauge just showed about 185 tops.
The engine does run a lot smoother, especially at idle. I used to have a bit of rough idle with the A/C on, but now it is smooth as glass, so I hate to "improve" it anymore and risk another problem. I can feel significant heat off the engine at idle, but not as much as prior to all of the cooling parts replacements.
I might give that temp sending unit a shot. However, mine seems to have a shielding gasket around it, and my experience with this old truck is that stuff like that breaks when you touch it, and finding those kind of replacement parts is almost impossible.