The best way to pin point the play is to block the rear wheels so it won't roll and slid under the front. While a helper rocks the steering wheel back and forth within the play. Closely watch each pivot point and joint. If you see relative movement in the joint replace the joint or tighten the taper retaining nut like on a tie rod end. You'll need to remove the cotter pin in the castle nuts in some cases to tighten it.
If you see the steering gear input moving but no pitman arm movement you have a limited adjust-ability in the box. You can only make this adjustment in the exact center of the total travel. Count total turns lock to lock and place the sw 1/2 the way distance. Eg 6 1/2 turns ltol means the center is 3 1/4 away from one lock. After finding the center put tape at the top so you can find it again. On the top of the box you have a nut with a threaded stud in the center that has either a slot in it or an allen socket in the top. Loosen the nut and screw the stud in cw about 1/8-1/4 turn at a time till you feel it begin to drag. Lock the nut and feel the slop. It should get better as you go in. At some point you will reach the adjustment limit and the steering wheel will develop a tight point when you drive that will feel like a resistance to return to the center. This it to far, so back the adjusting stud out a bit at a time until the drag is gone. That is all you can do with the box adjustment.
