My two challenges are 1) find a U joint 2) find the back piece of transmission casing matching what Pre '68 Dave has shown in his picture above. Otherwise I have to pull the engine or rear end to work on the clutch/tranny.
My best guess is someone put a 1948 to 1953 3/4 ton 4 speed tranny in your truck. The reason I say that is because the rear yoke is shorter, which is used in the 3/4 ton partial torque tube/open driveline. 2nd photo
The 1st attached photo is the type of u-joint you need. Note the longer rear yoke. The front yoke is hard to find.
Jorb, looks like you're right on a few points. I need a different u-joint assembly and the part in your illustration is nowhere to be found at the moment. If someone comes across this assembly, I would love to know about it. The transmission casing Dave shows earlier in the post would also be most welcome.
Refusing to send the truck to the junk yard, I'm going to try to get an alternate u-joint to work. Hope I don't need to work on the clutch before I find a solution.
A million thanks to all who responded. I'm an absolute newbie, desperate to put this beautiful old truck back on the road.