The old adage that you can't have your cake and eat it too isn't always true. Diesel Power magazine did some testing and showed that when it comes to converting your power-hungry belt-driven fan with a Flex-a-lite electric fan, that you can gain power and fuel economy. You can read the whole article at dieselpowermagazine.com.
The bigger and heavier the belt-driven fan, the more power you're going to free up. And you'll also see an improvement in fuel economy. The math here is easy: it takes more energy to spin a belt-driven fan than an electric fan. Another benefit of converting to a Flex-a-lite electric fan on your diesel truck is quicker warm-up times. That's like having you cake and eating it too, plus a side of ice cream!
You can find more information on the Flex-a-lite electric fan for '03-'08 Dodge Ram trucks with Cummins turbodiesel engines by visiting flex-a-lite.com.