As you're in the heart of the land of rust, to me, you have a couple choices:
- if purchasing locally or nearby, and doesn't appear to be a bucket of rust, I'd certainly want restoration photos so you're not buying a bucket of rust that was covered in filler then painted (while a magnet does help some in these cases, it doesn't catch everything; OR
- look for a relatively original paint truck from the Southwest or West Coast. This way you know exactly what you're getting and how many repairs you need to make, if any.
In any event, that's what I'd do.