Chevrolet didn't have a production line Tandem axle available until 1956. Before that every Chevy that was a Tandem had to be sent, when new to an outside jobber such as, Trucktor, Truckstell, Fabco,Grico, etc., for a conversion setup. My '54 Chevrolet Tandem pictured in the below link, had a Trucktor Chaindrive Tandem Conversion,
http://www.classiccoe.com/friends/spanky/1954%20Chevrolet5400-1a.jpg