As a direct answer to the OP's question, early-mid 80's 6.2 Suburban. Dirt cheap, inconspicuous, and reliable. Close 2nd would be same vintage F250/F350 diesel with the drawback of only having so much room in the cab for passengers. If Ford had the Excursion 20 years earlier it would have been my choice. I'm another that thinks that it's kind of a non-point though. Next time you're stuck in Portland traffic on a Friday afternoon because one car bumper tapped another, just close your eyes and imagine that X1000 but with no bridges. If there is a major natural or military disaster, no one is going anywhere. Stock up and plan to be camping at home for a good long while.