The owners manual said to break it in for 1000 miles, that's what I did. I made sure I had no prolonged steady rpm running, vary speeds, no high speeds, no high rpm's. The oil was changed at 900 miles because of a timing cover crack, or else I would have changed it at 1000 for the first change.
I plan on keeping this truck a long time, so the old, "Who cares, just beat the crap out of it immediately" routine does not fly for me. If you are going to spin your vehicles every year or two, then just rip it from day one.