Hy Beaver Bob, welcome, the SM420 came out in 1948 so there should be lots of them around setup for torque tube, you could find the tailhousing and "U" joint parts and possibly the output shaft and convert your transmission to a torque tube type, or trade your transmission for a torque tube type, or just buy a whole torque tube type transmission and rebuild it. Post an ad in the parts wanted forum farther down the page and see what pops up.
