I'm not super fussy on the size, as the truck currently has slightly taller tires on the rear than the front, which helps exagerate the forward lean. I can't recall the sizes I have on there right now.
What I'm really hoping for is some that are already mounted on decent 16" 8-bolt rims. I tried to find some at the pick-n-pull, but I think they strip off the good tires and sell them before the trucks hit the lot.
There's always one guy in the bargain finder that has his number in there all over the place. I don't know where he gets them all but he seems to have a lot of tires, lots of matching sets in different price ranges too