My unit is a 1965 which has a 1950 industrial as the power unit (4-53 GM Diesel). They were shipped with the driveline (rearend,tranny, Hydra-unit, clutch and motor) and dropped into the scraper frame.  My problem is in the trans. Let out on the clutch and it goes backward in top or bottom neutral.  Put it into a forward gear and let out and the locked trans will stall out the motor.  Shift rails and links all seem to move stuff like it is supposed to. Cant figure what is siezed where.