What do you mean "the torion bar is what really gives the feedback"? Only Mopars were built with a torsion bar suspension as far as I know.
To get the power steering assist, a spool valve has to allow hydraulic pressure from the pump to push on the appropriate side of the arm with the appropriate amount of force. The shaft that runs through the box is a fairly small diameter and as a result twists when steering force is applied to it. The spool valve is attached to this shaft.
When you turn the steering wheel at highway speed, there isn't much force involved so the shaft doesn't twist very much, and the spool valve doesn't open very much either, with the result that not very much assist is applied. When you're turning the wheel while parking, the shaft twists quite a bit, allowing the spool valve to open more fully and increase the amount of assist.
That is how the amount of steering effort is tailored; a thicker shaft twists less and generates less assist for the same amount of steering force applied by the driver. That makes for higher effort and more direct feedback. A thin one gives that '60's Mopar novocaine feel, where you can flip the wheel with one finger and have it turn a complete turn on inertia alone!
You can test the amount of torsional resistance your steering box has by turning the steering wheel with the engine off. The shaft will twist a certain amount before hitting the internal stops that prevent damage to that shaft; you'll feel those stops as they take the load and make a direct connection between the steering wheel and the front tires once the shaft has reached its maximum allowed twist. The size of the shaft affects how much force is needed to twist the shaft before it hits the stops. If you know how your steering feels or even better if you have a spring scale, you can test other boxes at the boneyard to see how they compare.
If you have a manual steering equipped car and one with ps, you'll easily be able to feel the difference; the manual box is a solid shaft as opposed to the ps box's twistable one.
I notice that they didn't include the numbers from what used to be the good box, which was the WS6 Trans Am box. I've used both and the Monte Carlo SS box is pretty close but is metric.
