[lower50's]

Chance not sure if I agree with the mechanical fan moving more air than a good electric. I got this off the Flex-a-lite sight:
"Since a belt-driven fan increases speed (and airflow) with engine speed, it can move more air at higher engine rpm - usually above 2,400 rpm - than an electric fan. Conversely, electric fans move more air than belt-driven fans at engine speeds below 2,400 rpm in typical applications.
One major downside of belt-driven fans is parasitic loss. It simply takes more energy to spin a belt-driven fan than it does to produce the electricity needed for a comparable electric fan."

And since diesels don't spin to fast and don't create much heat at idle. Any fan is useless on the highway. Just trying to help, might make it easier for you to build your cooling system and you won't have a tornado under your ass.
My 16" derale cooling fan is rated at 2100cfm. Bumper looks great.