You could use a 41 3-speed transmission, it was sychronized. Same gear ratio in high gear, 1-1 as the 4 speed. My 39 stake truck has a 3-speed. Bonus with a 3 speed you won't have to double clutch to shift. You could keep your existing rear end, torque tube assembly. Just a thought.

Rick


1939 Chevrolet Stake Truck