SM420 Trans U-Joint Question

I'm working on an SM420 with the enclosed u-joint. From what I've gathered in searches, these were used in 47-51 1/2 and 3/4 ton trucks. I can find a joint listing for the 1/2 ton but doesn't say anything about the 3/4. Are they the same? If they aren't the same, does anyone have the dimensions so I can tell what I have?

 

For GMC (and I assume Chevys are the same) 1/2 ton part numbers are different than 3/4 ton.

 

Dim memories here, there are different P/N's fpr 1/2 ~ 3/4 ton but maybe interchangeable.......

"Mothertrucker" in Az. will know and have them for sale......

 

They are interchangeable on the trans, but NOT on the driveline.