Gday mate, welcome to the forum.

I have to agree with the posts above, as much as a body swap is still not a small job, make sure you have the tools and safety equipment, a bunch of patience etc, if it's a choice between undoing a number of bolts, (even a large number of bolts) and some wiring etc or cutting a roof off and welding in a new one, I reckon I'd be choosing replacing the body.

In my experience rust repair is never fun... Always seems to be more rust than can be seen on the surface, and if a lot is visible on the surface, who knows how much extra work will reveal itself, will it all line up afterwards, will the windscreen seal properly, will the welds be weak points after many kilometres of corrugations, that sort of thing.

I don't know what the legalities are of either (if this is something you're worried about), maybe someone has experience here with the this?