manaen covered just about all of it.
intake and exhaust are 2 biggies.
flowmaster 50 suv is a very common muffler for the 4.0 but it looks like you have something else in mind.
as for intake i went with the volant. deffinatly not the cheapest option. but i've enjoyed it. when you look for an intake make sure it suits your needs. i went with volant because it's enclosed box design that's similar the OEM air box. i chose it because i love playing in the mud, the box keeps the filter safe and fairly clean unlike many kits where the fiilter is exposed.
if you dont want to drop $200ish on a good intake right now then i'd go with a k&n drop in filter and cut a larger hole in your air box. on the bottom half where it has it's TINY hole for air to come in just cut a large oval across that whole side. some advise against it. i never did it but i cant see how it could make things any worse. i'd look into it.
after that the next big step is flash programing not cheap... like $400 with a used programer. search some of these terms: sct, xcalibrator, tune, james henson, and chip. you'll find tons of info. make sure you have james henson do it. his site is
www.hensonperformance.com you can also contact him on this forum. his user name is jah81592.
as for lift, like he said, torsion bar twist for the front and shackles/add a leaf(aal's) for the back is good and cheap. it will allow you to fit some 31's with no rubbing(for some people maybe a tiny tiny bit)
next option is a body lift. i think you can get up to 4 in. but the down side is frame exposure. many people dont like the look, but a small body lift to clear larger tires is always good. also with bigger body lifts you may have to extend brake lines and your drive shaft...
and i think your next option is a suspension lift which is like $1,800 i believe...
i just graduated from high school. class of '07. got my truck when i was like 17 and a half. i've been modding it ever since. be careful, it's a nasty addiction. also be careful, these things can be tippy... i just flipped mine on it's side for the first time a couple weeks ago... $3,500 in body damage... any ways there are a few of us young guys here. old guys too lol they're very helpful. there's an INCREDIBLE amount of information on this site, all kinds of how to's, free horsepower mods, and helpful people. good luck!
oh yeah, when it comes to finding parts here's my favorite way to get the best price. if you have a specific part in mind then find it on it's manufacturers web site and copy the product number then go here
http://www.google.com/products paste the product number and search then arrange from lowest price to highest. you'll find your self saving a lot of money this way. also, a web site called
www.fasterthanthem.com seems to always have the lowest prices, by a significant amount.