If you go more than 2.5 your looking at replacing a lot more parts and possibly a SYE and new rear driveshaft. With 4 in you'll need new control arms, track bar or a bracket to drop the track bar, sway bar links, either an SYE with new driveshaft or you may be ok with a transfer case drop which is a lot cheaper. I've also heard the rear coil bracket can be at too much of an angle when lifting it that much and the coil can pop out. I just put 3 in springs in the front and 2 in in the rear. I have no driveline vibrations and all I've replaced is the shocks. I would recommend 2 to 2.5 you should be fine running 33s as long as you extend the bumpstops. If you want a little more lift you could do a 1 in body lift.