I've been doing some research into this vehicle. Originally I thought it looked like a larger version of the security truck from 'Money to Burn' (or Swamp Molly's arms truck). That's a 1969 Dodge P-200 Step Van. Eventually, after loads of searching, I found a couple of pictures of this van. Apart from the location of the turn signals and lights along the roof it's pretty much the same. It looks like it's quite a rare vehicle. The body is made of aluminum by Flxible Southern, and this one is on a 1966 Chevy P-30 chassis, although other chassis were used. The van on the left of this advert again has the turn signals in a different place, but other than that it's the same.