While the 4l80 is an awesome trans for that kind of power I would run a built 48RE. I have one in my Dodge that I got from Goerend transmission and its a beast. My truck is in the area of 350-375 rwhp and the trans isn't even phased by full throttle runs with an 8k trailer in tow, I only did this once and while the truck took it just fine it's not safe at all to do.. It just shifts hard and fast. It can shift nice and easy too which is good. It did cost me $6500 but that's with install at a friends shop and the 6 gallons of amsoil it needed.
I was told it could handle 600 rwhp, just no boosted launches(I don't plan on any nor will I drag race this truck). I only got the billet flexplate and input shaft. For any power or serious racing duty the output and intermediate have to upgraded to the billet pieces.
Sounds like ethir way I go its going to cost me about 5K which will be more than I have in the entire truck and 5.9 cummins! Oh well! Pay to play...
