I did the same repair on one of my cars..
Since the torsion tube apparently has not moved, You're pretty good to go, try to orient the plane of the mounting bosses for the spring plate such that they are square to the vertical plane of the tub, and parallel to the centerline of the car..
On the car that I performed this work on I did the front pan, both rear torsion areas, door jambs, kidneys, etc... and I'm able to align it accurately.. its between 1/8-1/4" out of square...Oh yea I did the longitudinals at the same time
I can't find pic of when I worked on the torsion tube area... however...
