steering gearbox problem

Well that points to sector shaft play then .
This is easy to adjust, but there is a specific way to crank it together.A little loose is better than too tight,in this case.......
The Sector has to be cranked down with the rack well-centered. The rack centered, not the steering wheel.
Some guys crank the steering wheel all the way to the left, and then the right, counting the turns and splitting it in the middle.Well if your steering stops are 45 years old, they may not be in the proper place, anymore. So this is a good STARTING place. After a preliminary adjustment,I work the pitman arm a few degrees in each direction to find the tight spot, and set the lash there.
Make sure the box itself does not move at all, on it's three securing bolts.