I did a complete fram off restoration few years back and during reassembly i installed a oversized radiator, fan clutch which the vehicle did not come with from the factory, a new temperatue sensor, thermostat, and what i am noticeing after driving the vehicle on the highway for roughly 30 minuites the red temperature indicator light comes on it may flicker, the light also comes on after the engine is ideling but once i accelerate the light goes out, im not sure if the engine is really overheating, if it is im not sure if the fan clutch is the cause because the original fan assembly seemed as it was closer to the radiator it had a extension on it, or is the temperature sensor the wrong one, coolant is not spilling over or through the radiator cap when the light is on, if anyone has the same problem and can share the diagnosis it would be great if you can share your knowledge thank you for your help stay safe and healthy

 

Verify with a known good mechanical temp gauge and or a handheld laser temp gun. Never rely on a light.
By the time it illuminates it's too late(for a real over-temp situation).

Using a handheld laser temp gun verify temp is by the sensor. Measure the upper and lower radiator tanks too.
I suspect you have a bad sensor?
Verify the systems holding pressure.
Verify the proper coolant level.
Verify the rad cap is good.
Verify the clutch fan is good. Viscus drive or bi-metal sprong type??
Do you have a factory fan shroud? You should. If yes is the fan depth about 1/2 way into the shroud, (1/2 the depth of the fan blades).

 

After verifying the temps are ok and your not overheating. Most often the other causes of this is an air pocket in the chamber where the sensor is mounted, a bad sensor, or a chafed sensor wire that's shorting to ground somewhere. You can disconnect the sensor end of the wire, put some tape on it and drive around and see if the light comes on.