I work for a cooling company and have found that getting an electric fan centered in the radiator is best, also having a good shroud is key as well. If you can fit a 16" on the inside of the motor compartment(this would be a puller),that would be the way to go.
Some of the electric fans on the market have a CFM rating but they can be deceiving too. We tested some fans and have found that they claim 3000cfm and after they are mounted on the radiator only pull 900-1000 cfm. Its due to static pressure created when the fan is attached , if you hold the fan above your head and turn it on, sure it will pull 3000, but when you apply static pressure to the mix, cfm is greatly reduced.
We have found that Spal fans have the least amount of pressure drop. There cfm ratings are 2750 and at the radiator still pull 2350cfm.