BFGoodrich All-Terrain T/A KO
Several of my friends have had good luck with these, the 33" range from 9.5 to 12.5 widths, max sidewall on most sizes is 50psi.
If your not hitting too many good sized sharp rocks you might consider an LT tire.
edit: When you go on your trails drop the psi down to about 30-35psi so the bumps don't beat you and your truck up... trust me.