Loose PS Box??
Check the steering box mount!!!
This is what I found when I inspected the steering box mount on my K frame. :banghead:
The entire box moved when you turned the wheel on this car, basically only one side of the mount was still attached to the K. I re-welded all of the broken welds, then added gussets like Firm Feel does to box the steering mount in completely.
Orange arrows highlight all the cracks. I've already made a few tack welds in these pictures to anchor some of the corners.