That is an odd driveline. While not impossible, it would be very difficult to source a "bolt-in" torque tube rear axle that matches the wheelbase of your project truck. I hope you're parts hunting skills are exceptional! It may be much easier to source an open driveshaft style rear axle and transmission as it would allow a much greater latitude in wheelbase options. I believe that the more readily available 1941-46 deco 1 1/2 ton trucks should be suitable parts donors for your model.
