There is the original Army Data Summary and Technical Description documents, but I suppose that there is nothing in them to definatively say that the vehicle is a Land Rover Australia Factory design, Vs a summary of Modifications that have been made by the Australian Army.
Does the vehicle still have the Compliance plate? It will be noted on there that it states the vehicle model is "Military 4x4", That is, it's not a Land Rover OneTen or Defender with modifications, but a unique model in itself.