'59 was the only year for that Dana/Spicer rearend in a Chevy. It was a Spicer 45, and should have a Positraction in it. The rear was standard with and without Positraction in GMC from '55-'59, perhaps later as well. The rear is more or less a Spicer/Dana 44, some parts do interchange, but not many.
With the rear you have saying "44" on it, good chance it's from a '60s model GMC, which stayed with leaf springs when Chevy went coil.
