Best way to get stripped nut off.

Ok thanks to the diagram I know exactly what it is. It is the Shaft that goes into the cross member. Is there a place to buy a new one or would it be best to just get one from another car? Sorry for the ignorance this is my first car with Torsion bars so I don't know much about them still.

If yours is bad a donor car part would be fine. It could just be the nut is stripped and the shaft is fine. Is there enough room to get a nut splitter in?

Don't sweat about calling the part by the wrong name because we all start there and learn as we go.