The 4x4x2 box is stout and fits well in a bronco, plus it's all ford-spec parts. It's the 4x4 steering box out of an F150 or 78-79 bronco, but with a 2wd ball nut/worm in it so it turns the right direction. On the donor 4x4 trucks the pitman arm points forward, on an Early Bronco, you switch it to point back. Without swapping the 2wd components into it, the truck would steer left if you turned the wheel right.
The locknut and stud you highlited in red on top of the picture of a steering box is the sector shaft preload adjustment. The sector is actually the gear inside that the ball nut meshes with, and the sector shaft is what the pitman arm attaches too.
You can adjust the amount of slop in a box with the sector shaft preload, but be careful because an old box will be worn more in the middle of the steering range, so if you snug it up it may bind closer to full lock steering.