In the 1954 Silver Book, Coleman advertises 4-wheel drive packages for shipping to the customer: 3/4 ton through 2 ton trucks (with single-speed rear axles only). The advertisement also shows a 4-wheel drive 1/2 ton Suburban.
Northwestern Auto Parts Company, NAPCO (in Minn.) also advertises 4-wheel drive with two speed range (same 4WD unit used in WWII military Chevrolet trucks). So, Yes, it was most likely available in 1948.
