OK...I know about that!?!
There is one adjustment on the top of the box that sets the depth of the drive pin in the worm gear. Taking the slack out of that may help a bit with play in the steering. It will not help with steering force. Other adjustments at the box requires removal of the box and disassembly.
By far, the biggest cause of hard steering is caused by bent vertical links. There is no adjustment for camber on these cars, so body shops are prone to bend the vertical links to set camber. Of course, hitting curb can also bend the vertical links, as they are not terribly strong. The problem with a bent link is that the bottom pivot is a threaded post in a trunion that only pivots one direction. If the link is bent, then it tries to pivot the trunion in a direction it cannot move...causing a bind. The links must be removed to be straightened.
Oh...one thought. If someone previously has over-tightened your drive pin adjustment on the steering box, that could cause hard steering. The worm gear is cut tighter at center. This is so the steering feels tight while going straight. The worm is cut loose off-center, but the car's natural tendency to want to go straight makes that play imperceptible. If someone has tried to remove the pin play with the box off center, then the pin will bind when near center.