You can get dually fender flares from Alamo Conversion Co (210) 647-1100 or CoachCraft Industries (541) 466-5131. And if you already have 4 wheel drive or two wheel drive and do not want to convert to a dually axle you can by these spacers from arrowcraft
http://www.arrowcraft.com/ to space the front out and then you can run dually rims all the way around. I would recommend getting a dually front axle or at least the hubs before running spacers in the front for two main reasons. The first is dually dana 60 fronts can be had for pretty cheap because there is no demand for them and second is spacers are not what I call safe especially on the steer axle. There is a reason most tire dealers will not touch your car truck or van if it has spacers installed, it is because of safety and liability issues. I am as guilty as anyone I actually run them on the back of my personal van but I check them regularly which is a pain in ******** and locktight them religiously. I like pretty much anyone that has ever ran spacers, have had them come lose on me and when they do it is not pretty because it tears up the hub the studs the wheel and this is if you catch it before it falls off. If it falls off you can only imagine the possibly damage at that point.
I think dually vans look killer I was going to do mine in duallys I even had the axles for it. But I talked my self out of it because I already have to pull in my mirrors when four wheeling and I knew the duallys would keep me out of trails I wanted to be on.