So far I've replaced full length floor pans under the front seats on both sides, three sections of floor pan under the rear seats, the entire trunk floor, the entire area behind the trunk floor, (the area outside the trunk, hidden by the rear bumper) both outer wheel houses, both rear quarter panels, (have the old ones cut off, still need to weld the new ones on. Waiting until its back on the frame for this.) And, I've moved the inner wheel houses in 2", plus narrowed the frame 2". I still have a few dents in the roof to fix and I plan to smooth out the firewall. I'd say I have around 400 hours in the thing right now.
I would never have started with this particular car (really bad shape) if it had not been the very same car I owned in 1974/1975 when I was in high school. Found it one year ago here in town after it had been setting for 28 years. It looked familiar so I did a title search on it and it was the very same car I owned before. It had 1976 license plates on it when I bought it.
I thought the inner wheel houses were easier, or maybe just less work measuring and bracing, than the frame was. Personally I would not have attempted it without it being on the rotiserrie. I bet I've spun the thing back and forth 50 times since I've started working on it. (Built mine myself for $168 worth of tube steel and $8 worth of casters.)
I didn't mark anything before I pulled the body from the frame. Did the frame first, then the body. Don't even think I measured back and forth between the two more than 3 or 4 times. Since I replaced the whole trunk floor the only body mounts that moved in will be new ones that I'll have to weld onto the new trunk floor anyway. So, I'll just line them up and weld them on when I put the body back on the frame the next time.
Let me know if you have any more questions or need some more pictures.