They're really only good for things like body panels, and maybe some interior bits after a thorough cleaning and sanitizing. All electrics will be trash, and anything mechanical would need a strip down to ensure its not full of water/mud/corrosion.
As said, the majority will never be on the road again, it's far too hard to satisfy the requirements, especially when it comes to newer cars with airbags, in which all of them, and their control units, need to be replaced.