A good place to look at some mounts is
http://www.premiere-electronics.net/
There are several that would work well on your van..Stainless is best, aluminum works pretty well too though..Firestik SS-204A or Firestik SS-274a mounts from that website might be good choices..Firestik SS-64AGM GM Sport Mirror Bracket MIGHT be a good choice too, but pay attention to what size antenna you put on it.. Try to spring for the "monster stud"..thats a good strong stud for mounting vertually any antenna you want.
Stay away from the fiberglass antennas ESPECIALLY the ones under 4 ft long, anything under that is going to be a very poor performer. If you REALLY want to use a fiberglass antenna, get a francis..they're the best of the fiberglass antennas..you'll need an external SWR meter to tune your setup no matter what you get. The wilson 2000 trucker is also a good choice for an antenna for 10/11 meter use..
Hope all that makes enough sense to be of some help.