Well it just depends on what you want. If you go with a 4-6" lift then you are going to have to put on some pretty large tires to make it look right. If you go with tires larger than a 33" then you will want to regear to bring it back to the right power band or otherwise your truck will be a real dog. You can fit up to a 35" tire with the 2.5" leveling kit. The leveling kits are easy to install and don't put that much stress on your drive train. There are a lot of people running the 2.5" leveling kits with no problems at all. I love my my leveling kit and how it makes my truck look. I sit a lot taller than a stock F150 and it's just the right amount of lift. I installed 33-12.50x17 Cooper STT mud tires on too and they are the best mud tire I have ever ran. They are great in the mud, quiet on the road and good on snow and wet pavement. The leveling kit was $100 and the tires were $1200. I am running factory wheels right now but will be replacing them very soon. Here is a pic of what my 06 F150 looks like with the lift and tires.