You may be right about the steering box bolts being fine thread. I do know the one that screws up into the box is coarse thread. If you're using stainless steel fasteners, be sure to use anti-seize on them. Especially any that are fine thread. Stainless tends go gall when the nuts and bolts are threaded together and ruin them. But be careful that you don't get any on you.
Good advice. I put something on just about every bolt. Anti-seize, blue, red, or green Loctite. I use the little sticks or tubes of anti-seize and Loctite when possible. So easy to use. Especially the anti-seize. The jar with the brush is a mess.