I have a '72 Caprice and it came stock with a clutch fan and shroud, I had a 16 inch flex fan, so I tried it instead, and it did NOT move as much air. I put the clutch fan back on, also if you notice clutch fans cost twice as much. The only bad thing about a clutch fan is thier more heavy, but in less your building a race car a little weight will not hurt. Forget the fan thier are many radiator coolant additives that can lower your temp by 20 degrees. What kind of carb. are you running?