The passenger van has a lot of windows for you not to stand out if you don't want to give a burglar a reason to take your stuff. Cover the windows and you call the attention of the police. I would otherwise advise against the conversion van due to the bulk of unnecessary stuff. If you're going to gut it anyway then get the passenger van for less time, money and energy - although you could sell parts from the conversion if possible. They are ice boxes in winter and a sauna in summer so a little more space (without an AC) is ideal with the passenger van. It's also lighter so you'll get better mpg.
Take them both for a test drive. To make the ultimate decision take both to a mechanic to take a look, should be no problem for the seller to allow you to do so. And finally do not pay the asking price. Don't low-ball them but do not pay asking price. Offer $200 less, cash, at the right time.. they really want it sold, and most likely added that $200 to begin with. That's business. Good luck.
Also don't store the batteries in your cabin as they release toxic fumes from time to time.
