Do you already have the motor?? If not why not go with a 6.0.. Might as well go big the first time and not wish you did..Ive got a buddy with the l33 and even though it runs nicely esp after we tuned it.., i think the 6.0 would still be a better starting point.. If already have the l33, and plan to add a turbo, probably want to look at a FLT tranny or even a 4l80e.. the tranny is definetely the weak link in these trucks.. good luck on whatever you decide..