What you have there is a SM420. I had a torque tube (closed driveline) in my 54 with a SM420. I got a SM420 out of a 1967 truck and it bolted right in place of the old one. The two transmissions were identical exept the later model had the yoke like your pix. Bonus: the 67 has a switch for backup light(s). The next trick is getting a new driveshaft. The new driveshaft needed to be just over 64" with a slip joint. I couldn't find a one piece 'shaft that would work. The guy at the local driveshaft shop told me long ones were really hard to find and he suggested that I bite the bullet and get a two piece 'shaft. That's what I did, so I had to make a mount for a steady bearing... The good news is that I have a modern posi rearend and have lots of gear ratio choices!

Logically, if the transmission in your 45 is compatible with the 54 (I don't know if it is), then the trans in your picture should work.

Gord
1954 1/2 ton 235 4 speed