The other major drama with some NOS stuff that has been around over the last 20 years is lots of it came out of reject stock held in containers at GMH. People bought the whole containers full of reject parts, and they were rejects for a reason. As an example I bought a NOS HK Monaro tail-lamp assembly on Ebay 15 or so years ago, it was cheap and as it was Monaro not GTS the alloy housing was of no use to me but the lenses were and also being NOS it still had its original red paint on it so I could use it for colour matching for the GTS tail-lamps and boot moulding. I tried it recently on a HK Kingswood (as these are the same as Monaro) and surprise, it didn't fit properly! It was a reject part for a reason.
I've seen a lot of NOS door skins, panels etc that were also rejects. A lot of the NOS Torana stuff that was around will be the same, poor buggers that paid $2000 for an LC grille for example would have got a rude shock when they tried to fit it. The best stuff is old dealer stock or from old panel shops.