If you haul non-placardable HAZMAT, meaning placardable in amounts greater than 1000 pounds (from a single shipper), but not placardable in lesser amounts, you still have to have a HAZMAT endorsement on your CDL.
Cargo van CDL's are Class C with either a HAZMAT or Passenger endorsement. A Class C without one or the other endorsement doesn't exist.
Incidentally, HAZMAT that is placardable in any amount (inhalation hazards, most poisons, explosives, etc.), generally cannot be carried in a cargo van.