Electric Fan Q&As

Hi,
Im thinking of getting an electric fan for my 72 Duster w/ 360 and need advice.What size of fan should I get(12 inch,14 inch,16 inch?)and what CFM?Also,how do I wire it?Is there a way I can wire it without a temp switch,but just use a relay and a toggle switch?Do I need to do anything to my electrical system since they do seem to have a big amperage draw?thanks everyone:cheers: