I don’t think there ever was such a thing as a DU-5 as described by this American magazine in 1955 but as this was prior to official exports to the US by Nissan, they could be forgiven for having little information available to them. I believe that the model shown in this short piece is a Datsun 6147 which went on sale in Japan between 1953 and 1954. This model was very dated looking and owed much of its design and styling to the pre-war Datsun 13T of 1936.
The 6147 came as a regular pickup but this version had a double cab making it a four seater, albeit a very cramped one. I’ve also seen this body style referred to as a ‘Ranch Sedan’ by another American publication from the late 50’s, although I doubt it would have been known as that in Japan.