Possible sources of rattles (and solutions):
*Change and other shit rattling around in your truck (happens many times that people don't check)
*Loose parts (locate and tighten with loctite)
*Interior/Exterior trim pieces rubbing (locate and either secure the pieces away from each other or use some felt/weatherstripping)
*Moving parts rubbing (relocate and/or grind parts for clearance if necessary)
The main thing here is that if your truck rattles and it bothers you, track down all the little rattles and do what it takes to fix them. My truck only has one rattle and a little knock, and I haven't gotten around to fixing them yet, but I plan on doing it. The rest of us, who aren't bothered by rattles that aren't indicative of mechanical problems, just turn up the stereo and live with it.
Wolfpack, I realize that you feel we aren't being helpful, but we've given quite a few general guidelines for locating and fixing noises, and have also had some viewpoints on the "if it makes noise, turn up the stereo" front. Everyone is entitled to an opinion, and I haven't heard a single "google it yourself" post yet. I haven't heard Zero complain about us being less than helpful, and his opinion is the one that matters on this subject most, since he is the OP. We are all here on this site with the understanding that it is geared for the more hardcore offroading scene with the GMT360, a scene that is much more tolerant of squeaks and rattles than the OS, and so some of these responses are expected.
/end rant
So Zero, the items I have posted above are how all service departments and dealers approach what we call NVH (noise/vibration/harshness) problems in cars... basically the hardest part is finding what the noise is coming from, and once you do that, tightening/adding felt/grinding (in the case of modified vehicles) fixes the problem. Another thought is that maybe adding the beefy tires increased the vibrations, making squeaks and rattles that were already there more apparent. If this is the case (most likely) then just find them and fix them. I know when I lifted my TB, I had to go back and make sure that everything was sufficiently tightened, and the rear shocks shimmed properly, before all the noises went away.
Good Luck
-Phil