I've seen that done before on a torque tube where they spliced in the overdrive right before the rear end. I think it was a borg warner o.d.
Not the whole trans, just the o.d. section.
They welded a small sprocket to each end where
the drive shaft was cut and butted them together
and wrapped roller chain around them. It left
a small amount of play so the joint would not snap under torque. Looked pretty neat.
I saw a short article on this in the book
"How to Restore Your Chevy Pickup" (I think that was the book) There is a company in the midwest somewhere that does this conversion.
I am just going by memory and may have missed a
few details. I'm sure a lot of other bolters have this book and may have more to say about it.

Steve

'49 3800
'52 3600
'57 3100