I had the steering system off recently and opened up the box to inspect the gear mesh and bearings.
As Mach1rider desribed, CW on the threaded stud "tightens up" steering box play and CCW loosens it. The Ford shop manual describes setting the adjustments to a maximum inch-pound drag reading throughout the steering's lock-to-lock motion. The proper adjustmented measurement is so small it would be difficult to measure without a dial-type inch-pound torque wrench. Also, this adjustment is also supposed to be done with the pitman arm disconnected from the center link/control valve.
If you can isolate your steering slop to the box and suspect it is worn internally, you've got nothing to loose by tightening it down some, but if the gears are too badly worn, no amount of adjustment will remedy the slop.
I ended up buttoning my box up too tight and having to re-adjust (loosening off some), but am personally accustomed to R&P and wasn't happy with the slop.
Also as noted, this system is antiquated, and expecting it to behave as a new car's system is an unfair comparison.