If you want a project to work on and can weld and don't mind bodywork or have a buddy who can help, then just buy whatever is cheapest lol If you CAN'T weld or hate doing bodywork, then buy as nice of truck you can afford..rust free being key. Mechanical issues are always easy to fix and learn how to fix and cheap compared to paying somebody for bodywork.
But when it comes to old chevy's majority of them have rust in the rocker panels, kick boards, floor boards, cab corner, bottoms of fenders and around the windshield chanel. Those are common areas.
Just expect to pay good money for something that's ACTUALLY rust free. I search within 500miles of my house for trucks and drive all over looking at them, but you have to have the time and patiences when it comes to finding the right project.
Nate