Here is a SM420 transmission.
Zach (443) 907-7131
Listing is in the eBay, CL forum under; SM420 transmisions and PTOs
It is an older ad, so if you're interested I would call soon.
The transmission has the rear bearing retainer cover for the torque tube and what looks like a 1/2 ton front yoke w/attaching bolt.
Maybe the guy would make a deal for both.
All can do is ask, the worst he can say is no.
All you would need after that would be rear yoke, trunnion & ball housing with 4 bolt hole ball collar.http://chevy.oldcarmanualproject.com/1929_57chevyparts/57cmpc0341.htm