The thermostat controls the minimum operating temperature only. Use a high flow thermostat. 60%water 40% coolant and a bottle of wetting agent. Today's gasoline is very different from 1970 and is designed to run in engines running 200-210 degrees.

Thru the use of instrumentation[air-fuel meter] it is observed that when the operating temperature is below 195 degrees raw fuel will collect in the intake at idling & low rpm and burn off at cruise making the a-f rich then lean.

The old iron runs great at 195 - 210. 210 is not hot, 220 is warm 230 is hot.

Lot's of wives wagging their tales here.