Torsion bar removal

First point... Impact wrench will not work. The rotating hammer effect it has is lost in the movement of the nut block.
Second point.. many years of stress distorts the threads in that nut block as much or even more than the bolts threads within it.
Third point.. it is a replacible nut by design.

If you are rebuilding suspension...
You could...
Take the lower ball joint apart. Take the strut rod apart. Take the lower bushing pivot pin apart. Drive the entire lower arm assembly rearward.

If your task is torsion bar replace only... Cut the adjust bolt above the nut block.
Don't be surprised if the torsion bars are still frozen in place. If so the rebuild suspension method will be required. Good luck with it