There was a 5 speed Clark with OD that will fit, but then you would need a different PTO. An auxiliary is another option, but they are heavy and take up a lot of room. You may can get a later 3/4 ton third member to bolt into your banjo housing. I am not that familiar with interchangeability of 40's Chev. Around 50 MPH is probably all the horsepower and brakes you have anyway.