Personally, I wouldn't go the full frame route unless you have rust problems, seems like a lot of work. The folding rear seat back is partially plywood and is quite heavy. Same for the trunk divider, but you will have to replace it with a metal firewall to isolate the trunk if you run a fuel cell. I would remove the door panels and replace them with thin aluminum. You can't leave the holes in the doors uncovered due to sharp edges.