Confused what to do with a 5.9L serpentine setup

Someone mentioned the March set up(serpentine). I purchased a March "underdrive" set years ago for my 99 Dakota. That has been sold, but I kept the water pump under drive pulley. I run a Magnum 408, in 75 Dart Swinger and have a 3:91 Sure Grip. Use the original size 75 radiator and it does not over heat. Even at 75 mph @ 98 degrees.
If the under drive is still available from March or anyone else, It may be your solution.