Find out the thread size in the intake and then you can buy the adaptor. You can then buy it online from there, should be about $10.
I ended up putting the fan switch in the thermostat housing and the temp gauge sensor where the idiot light switch used to be, on the back if the head at the firewall. We are measuring about an 8 degree difference between the two locations when the system is flowing and the thermostat is open. So basically the temp gauge reads a little low.. Good enough. Would have kinda liked to keep the idiot light.