What Patrick said. It really doesn't look as bad as I was afraid it might. After the '68, this will be a walk in the park for you!It does not look that bad. Are you going to replace the inner wheelhouses? They seem to look ok. A lot of the rear part of the car is welded to the inner wheelhouses. Things could start moving if they are cut out and the remaining parts are not braced.
The frame rails look rusty on the outside. How deep is the rust?
Take measurements of the convertible trunk gutter brace. Measure from the brace to the trunk pan where the cocktail shakers bolt onto. This brace could move when you cut the outer wheelhouse out.
I likes the garage a whole lot!