There's my 4x4 stock height with 31x10.5x15s. You should be able to run that size tire with your truck with no problems at all. You probably won't even notice the difference. They won't make your truck look super super aggressive, but they are a good size tire and would be a nice addition to your truck.
33s would probably be the most aggressive size you could fit on your truck, but with a 3.0L and 3.73 gears I wouldn't reccommend it! My truck had 4.10s and a 4.0 and the 33s made it a bit sluggish off the line. My recommendation to you is to go for the 31s, or if you can afford them, 32x11.5s would be feasible also.