recently purchased 1979 f600 4x4 with rockwell axles and transfer case, must be one of the earlies ford factory 4x4 installations in medium duty class. not sure on trans, code m, think it is 5 spd clark. has 370 big block, p/s hydraulic assist cylinder on pass wheel and p/s cooler under hood. truck is double framed and has 6,000lb autocrane mounted on rear.