[IdahoJeeper]

The temp switch kit that comes with the Flex-a-Lite fans says its sensor installs in the upper hose right at the radiator... I thought that was strange, but maybe they have something figured out. I also wonder if you could install it in one of the block drain or freeze plug holes. "Dammit Jim, I'm an electrician, not an auto mechanic!" (sorry)
I wonder if a person could pick up a gauge and the appropriate sensor if it could be installed somewhere else on the block that has access to coolant. You'll need 12V noncontinuous (on with ignition) power.
Jasper brings up an intriguing idea, albeit overkill for a permanent install-they do make a 12V panel mounted temp meter for industrial applications (I'd have to research it) which uses the thermocouple to give you a readout. I suppose one of those could be installed... I'll see what I can find!