This is how I ran the thermostatic switch for my electric fans on my '68 Camaro.

I don't like a lot of wires and junk hanging off my engine. When I have to add something I try and see the cleanest way it can go, even if it's more difficult than the normal process.

I got a new radiator and fans for the Camaro by Be Cool. This particular setup used a computer that controls the fans. The computer uses a water temperature sensor to turn on and I had already used a hidden water passage to install my water temperature gauge.

I ended up welding a bung into the radiator to screw the sensor in. This wouldn't be ideal for a normal water temperature gauge because it wouldn't read the engine's temperature with the thermostat closed and you could potentially overheat if you had a thermostat problem with no warning. It is great for the fan switch though because you wouldn't need the fan on until after the thermostat opened anyway.

I used a pipe thread bung and welded it in with my Lincoln TIG welder. It was really easy and works great.

Source:
Earl's Plumbing
www.holley.com