That is really a civilian Power Wagon body with modified bed for the tandem wheels. The WC63 is really open cab. As seen in the picture.
Really nice looking truck though. I know a guy now deceased that built one of these civilian 6x6's. It looked just like the one in the video even same color, actually I thought it may be the one he built. Maybe the guy Jay is interviewing just put the Cummins in it.