Water temp in Magnum (crate motor version). Where to place probe for gauge? Temp switch for fans?

Probably another noob question-- I have a probe for my water temp gauge and a switch for my electric fans.
One should go in the manifold...what about the other? Does it matter?

I'm not sure if it matters or not but the car is a Magnum 300 crate motor with LA style waterpump, etc. Mopar M2 manifold...

Thanks for any help and for not laughing at my endless ignorance. :D