MIght look inside the car, too, as mentioned. In the C-pillar internal areas, the turnk pan, and rear floor pans. Everywhere the water from above could have gotten to on its way toward the ground. Taking out the interior will be necessary.
As the roof is a structural part of the body, all of that "gone metal" means the body is weaker. Any project to replace the roof would mean the body has to be supported (on a flat floor!) on about 8 jackstands. Two under each side of the rocker panels, two for the front stub-frame, and two for the rear body/bumper crossmember. That would keep the body from collapsing when the top section is removed from it.
There might be some attraction to the existing car, but the reality, to me, is that the car you have can be a donor car for another car whose engine and transmission have been removed from it. A car with a better roof and hopefully never had a vinyl top covering on it.
Just some respectful thoughts,
CBODY67