Don't understand question. If you want a switch, just wire one in and install it in your dash, or for that matter, if you want to get really simple, just install one inline with your sensor in the engine compartment (although I don't know why you would want to do that).
On my 67, In installed an aftermarket electric fan. I have both a swiitch in my dash, and a variable resistor for the sender that I can vary from turrning the fan on on from 160 to 210 F. I even calibrated it and put the degree markings on the resistor that is mounted near the radiator and has a sensor that fits between the fins on your radiator. That way, I get warm in winter and keep engine temps down in summer. Don't get the kind that strap to your upper radiator hose, I did not find that one to be as reliable as the one with the sensor in the radiator fan right underneath the upper hose intake.
The switch on the dash is ONLY to turn the fan off, and the alternator off for 12 seconds at a time, if you know what I mean.
All this is available at Summit