Novak Transmission guide to SM420. If you have an enclosed driveshaft 4-speed on a 1948 or later 3100, it is almost certainly an SM420.
I have never seen a torque-tube to to open-drive-shaft swap kit (as a packaged full kit) - most people try to find a 1955 or later SM420 "open" rear-cover and "open" u-joint assembly. Maybe post a want ad here in the Swap Meet, or check eBay, or
find/use a craigslist nationwide search engine? If someone knows about a "packaged" swap kit, maybe they will post manufacture/vendor information?
In your first post, you indicated that you want to "retain the 6 lug wheels". The original 1950 3100 6-lug wheels? What open rear-end are you considering?
