Jerry I'm no 67-72 expert but since your in Texas you should look for a rust free truck. They aren't as abundant as they once were but they can still be found. Just keep in mind it may be a Texas truck now, but that doesn't mean it was always in Texas.
Beyond cab corners and rockers, another place to watch out for is above the windshield. If it has rust up there it's going to be expensive to repair. Look at the frame too. Although they normally don't rust severly unless before the cab does, you better check it regardless....
