recently purchased 1979 f600 4x4 with rockwell axles, transfer case. must be early factory installed 4x4 in medium duty class. not sure on trans, think its a clarck 5 speed. trans code is m. 370 big block, 6,000 autocrane mounted on rear of truck. truck is double framed and has hydraulic power steering assist cylinder on pass side wheel and has power steering cooler under hood.