I have the thunderbird fan the is suposed to pull around 4000cfm. Along with a fan relay setup from a Volvo. All I need it just a temp switch to tell the relays to turn on. The temp switch will be for low speed and the ac will be wired into the high speed. I will have a switch in the cab to run both low or high (incase the temp switch fails) along with led indicators to light up when either speed Is on.

your fan will run more often with the temp sensor on the inlet of the radiator as the temp will always be higher there then if it got the reading after the rad.

but that said the instructions for the kits all say near the inlet of the radiator