Interestingly, I have never found any ideal/target operating temperature for my '68 in any of the documentation.
They do mention a few temps in devices that help control or monitor temperature.
- The stock thermostat was 190F (AMA Specs and both manuals) and should start to open +- 7F (Diagnosis Manual) or +- 7F for used thermostat /187F to 193F for a new one(Service Manual)
- 190F Thermostat should be fully open 25F above it's rated temp. (Diagnosis Manual) or 222F (Service Manual)
- TVS will operate at idle temps above 230F to advance timing and reduce temps. (Diagnosis Manual)
- Using the correct 15 lb cap for pressurization boiling occurs in the correct coolant at 258F at sea level. (Diagnosis Manual)
- The temp idiot light does not illuminate until 248F +-20F. (Diagnosis Manual)
I only have an idiot light and have only seen the light after a thermostat failure and a sending unit failure in 52 years (and perhaps it's first water pump failure in the early 70's - I can't remember). I have occasionally turned on my heater to help the radiator when caught in stopped traffic in extreme summer temperatures as a precaution.
