It must not be listed anywhere. I'm not in the market but I'm a fan so I did a pretty good search of New Hampshire for this van, mostly to try to find more pics and better answer your question. I couldn't find it, which means maybe others can't find it. That's a good thing.
A couple things I'm seeing from the one pic though. Looks like rear windows have been added which means it may've started life as a basic cargo van. Many 7.3's did. If that's the case it may be a bare bones van with no cruise, tilt, power options (windows, door locks, etc), basic radio, all that. If so I'd probably pass. Not because a 4wd 7.3 isn't worth the price but because for 20k you ought to get these basic creature comforts. They make a van MUCH more livable. For instance, you can't reach across the van to roll a window down or unlock a door. It's too far for anyone short of NBA reach.
Keep us posted!