Unless the parts are relatively new I would replace the pitman arm and the idler arm. I replaced mine years ago, but still had some play in the steering. I drove it that way for 100,000 miles. I finally adjusted the box and that truck has never drove this good since it was (almost new) to me. I adjusted the over-center preload about 3/8 of a turn, and that's all it took. Since your inspector says that it's definitively the gearbox, I would try fixing instead of replacing. Several other of my steering components have been replaced over the years to fix worn out components, but it always had more slop than it should have. I had power steering leaks and finally replaced all of the hoses which fixed the leaks. Those crimped hoses just start leaking eventually. It will be interesting to see what you find that may have some wear & slop.