I'm with Reducto: Get the best van you can -- the color can be changed.
You could add a clamp-on roof rack and a sheet of plywood painted white to deflect overhead sunlight.
A roof vent (or two) is critical if you don't want the heat trapped inside. It stays inside a long time past sundown. (I learned this fast in the desert summer, and it was the first thing I added when I bought a ventless van.)
The next thing would be a floor vent using a marine deck plate (I saw this somewhere else here at CRVL, and put it in my Favorites). With this, you could take advantage of natural convection: the ground under the van is shaded and cooler (esp if you parked early), the cooler air comes up through the open vent (screened against cats, rats and opossums), rises as it heats up, and goes out the open roof vents).
https://www.amazon.com/s/?ie=UTF8&k...qmt=e&hvbmt=be&hvdev=c&ref=pd_sl_7lb1gwvrnv_e
JUST BE CAREFUL WHERE YOU INSTALL IT -- like not right over the gas tank, etc.
You could increase the air movement with a fan in the roof vent. Bob likes the "Fantastic Fan... it draws about 3 amps of power at 12 volts."
https://www.amazon.com/s/?ie=UTF8&k...argid=kwd-101410801989&ref=pd_sl_31sim6o0or_b
I've seen a couple of people who installed two roof vents with fans, and have one sucking air in and the other pushing it out. While this
moves the air, it's not
cooling it at all. This seems less advantageous because they're on the same level and they're sucking the same hot air in that the other one is blowing out. I would prefer to draw COOLER air in from down low, and get rid of the warm air.
You probably wouldn't have the fan running while you were away from the van, but if you had the vent open, natural convection would still be moving air through all day long, and it would be cooler when you went back to it than it would be without any vent at all.