There was a technnical article about this on Jim Carter's website a few years ago (it does not seem to be there any more). As I recall, the article stated that the 50-54 Chevy automobile/automatic (Powerglide) torque-tube rear-end (3.55) fit OK under the truck chassis (as far as width and length went - I do not recall the modications needed for spring mounts).

Also, I dimly recall that it was possible to substitute earlier (1948/1949)6-lug Chevy automobile rear axles into the later automobile 3.55 torque-tubes (that must have had 5-lug axles).

Please forgive my posting the above information - it is almost useless because I have no first-hand knowledge AND my memories have always been questionable.

Tim