Take a peek in the suspension section or due a search on torsion bars. Generally adjusting the torsion bars will give you more clearence for larger tires. You can usually raise the front about an inch to an inch and a half before your going to start changing hardware.
Get under your truck and look at the back of the lower control arm. You will see a bar that is attached to the back of the arm. Follow this bar back to the cross member. There are two holes in the cross member that have a bolt that is accessable. Tighten the bolt, raise the front. One turn is equal to about 1/4" in height IIRC. Raise the front end off the ground first, it will make the bolt easier to turn.
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