I got my F-350 pitman arm installed today. I had to cut a 1" section out of the F-250 pitman arm to get it off.
With the F-250 pitman arm and the Dana 60, I was able to turn 2.5 turns lock to lock and was about 1" away from the steering stops.
With the F-350 pitman arm and the Dana 60, I am now able to turn 3 turns lock to lock and hit the steering stops on the axle. It is amazing how much more turning radius that 1" will give you.
Here is the comparison of the 2 pitman arms. Obviously, the F-250 pitman arm is on the right and the F-350 pitman arm is on the left. I would say the reason the F-350 pitman arm gives you more turning radius is because it is about 1.25" longer center hole to center hole than the F-250 pitman arm. It is obvious in the picture that the F-350 arm is longer.
Here is the section I had to cut out of the F-250 arm to get it off the steering box.