The one I seen used in an apartment seemed to a decent job. It is a single hose unit, so I was thinking that in a van it would be more than enough. The way I would do it, is to place the unit, cut the hole and run a short piece of the hose to the outside. Another option would be to also duct the input to the outside of the van.
The 5000 btu option mounted in the rear window would be the easiest option, however I plan on mounting the generator on the ladder rack at the rear of the van, and concerned the the AC would be sucking in the exhaust from the generator.
The other mounting options for the window units, would be mounting it in side the van and boxing it in, but that seems like a lot of work, I have watched several You-Tube videos on the subject.