I saw it on Hemmings. It's at a Used Car lot, so I wouldn't expect them to get the series correct. It looks to be a 6400, or 6500 series with a Trucktor, or Truckstell Tandem conversion. It's a '51 Chevrolet.
Spanky Hardy Collector Of Fine Old G.M. COE Trucks & Antique Holmes Wreckers