I used a core BB engine from a '78 Cordoba with a very aggressive 7 blade clutch fan. I'd look for one like it if that's what you need.

I agree with the post above - from experience. The big fan will help with cooling problems when stopped or moving slowly. If your engine won't cool off pretty fast at speeds above 35 MPH you've got other problems a big fan won't solve.

If a good cooling system starts running hot at speed it almost always means the radiator is getting plugged.

If you're starting from scratch with a new system, it may be an older plugged radiator or too small radiator causing the problem or something else... what are the symptoms?