I'm the 3rd/4th+ owner of all my Zs. This should be good.
280z:
Floor repairs. THIN, like almost paper thing, metal, screwed over the holes. bondo varying in thickness ranging from 1/16 to 1/2". Only bondo on the car, thank god.
Carpet - glued onto all the rear interior plastic panels. When I was working on the car, I noticed my arm turning black - it was the carpet. Trashed.
Wiring. There were switches with wires that went NO WHERE. I thought one switch was for the fuel pump, and being a 16 year old noob, I thought I accidentally pulled the fuel pump switch when taking the center console out because the car didn't start right away. So I proceeded to take the whole car apart - dumb idea.
RTV is not for holding on the drip rail trim.
That's really it for that car. It wasn't bad.
240z #1 (now scrapped): Just one - body work. Originally a CA car, then came to the east coast, and apparently rotted out. Things I found - riveted on rockers, new rear 1/4s brazed on over top the old one at the top. Very poorly brazed on. Alignment, welds, etc. Lots of bondo. Some things weren't welded at all. Holes in front upper frame structure fiberglassed over. Some VERY poor attempts to weld up holes in the frame rails. A 1/2 bolt going between the TC rods.
240z #2: RTV and plexiglass is not the proper way to seal off the hatch vents, OR putting on the interior hatch panel. Past that, nothing horrible. Some thick bondo, nothing major as far as I can tell. Floor pan patches could be better. Not awful. Sure would be nice if the doors actually lined up though. I think the car was hit, and improperly fixed. I really hope it was just the door alignment, or the repairs are going to be $$$$$. The paint on the car could definitely have been done better.
Just because it works doesn't mean it's a good idea.