Check the springs like people have already suggested.
If you are just looking for an inexpensive way to get 33's under your rig, just do a body lift. They are little more than $100.00
It worked for me, was easy to do, and I have 33x12.5's that fit nicely without any real rubbing to speak of.


'91 Trooper
3.4 V6, K&N, 33x12.5 Trxus MT's, Aisin hubs, 3" body lift, Rear ARB Naches Trail