either the bushing is torn, or perhaps it has poly lower bushings, which will cause the piviot shaft to try and rotate, either way, remove the torsion bar, and from the back, and thru torsion bar socket of the LCA you can hammer the pin forward, tightening it up in it's bore on the K frame to try and release the nut, a little heat on the nut might help also, if the LCA bushing/pin is that bad, you might be able to pry the arm off it after pulling the torsion bar, then address the issue with the turning shaft