I guess to fully answer your question, we need to know a few things.
1. What do you want from your hopups-performance, durability, looks?
2. What part of the truck do you want to start with?
Forward Only Conversion (FOC) it removes the reverse gears from the transmission, and replaces it with a forward only gear. The benefits are: Lighter, less rotating mass, and better jump/response off the line. I never really used reverse, so when I installed the FOC, I absolutely loved it. One of the best things I did on my Maxx.