I have the 4+ u bolt flip kits front and rear. Yes they cost alot but they work great and moves everything up top so you dont get hung up in the rocks. That being said... My truck is primarily a trail rig. Yeah I drive it back and forth from Summerville to Mt p and to the beach in the summer but it rides like a trail rig. Not for the faint of heart. I drove it to the crab boil and thats about as far as it will ever go. My max speed with all my mods is about 60-65 so I stay off the interstate. Before you order a single part you need to sit down and figure out what you primary goal is with the 40. Some things to consider:
1- daily driver or trail rig?More of a daily driver. 75%
2-how many road miles will I put on it if it is a trail rig?
3- what am I willing to spend? $1500
4- do I want it to look good or wheel good? Both
5-does function or ride quality matter most?Both
6- body work or mechanical
When you figure your budget for your build, the max that your willing to spend add anothe K at least. When you do the lift there is always going to be some thing extra you didnt think about. In addition to all the obvious stuff you have to remember the little things like extended brake lines (go stainless) ,caster shims, drive line angles, and the possibility you might have to get a longer drive shaft.
Go through the truck with someone who knows them and identify all the issues. Make a list and prioritize. Get it road worthy and go from there. I learned the hard way and did alot of work in the wrong order.