Check the pitman arm and make sure it's tight. Also the drag link and tie rod ends. ball joints could also be suspect.

In regards to the steering box adjustment, meh, I don't reccomend it. It works great if the problem is in the steering box gear lash. If it isn't, you end up with a truck that wanders and is more difficult to correct beacuse the box is too tight. I know from experience and it sucks.

I had this problem three years ago and it turned out to be a worn pitman arm and bad tie rod ends.