Electric fan thermostatic switch location; radiator or intake?

[derotoreut]

I am trying to figure out where is the best place to install my dual electric fan thermostatic switch. Should the switch be installed into the radiator or the intake manifold? I have the capability to install it in either location. My aluminum radiator (from Wizard Cooling) came with a welded coupling, which would allow me to install it into the radiator. Or is it best to be located at the intake manifold?

FYI I have a 383 stroker putting out 465 HP. Currently I have the thermostatic fan switch installed in the welded bung on the radiator, but I don't know if this is the best location. I did this so I could install the temperature gauge sender at the intake manifold (because there is no location on the block for it). Please chime in on this too, because this may not be the best location for a gauge sender.

I am running dual SPAL 13" fans with relays off of the single thermostatic switch. I also have a trinary switch installed in my Vintage Air AC system to control the fans. Thanks for your help.