It can be done, but is a ton of work. What you'd have to do is cut the frame head off and weld on a torsion bar frame head. From the bulkhead where the master cylinder bolts on, rearwards, the std Beetle pan and the Super pan are identical.
I have a friend in CA that did this. He took a 72 Super pan, hacked off the frame head, welded on the torsion bar frame head, then put his 69 body on it.