You certainly can install it either way obviously and it won't matter. I have worked on several of these and never seen a rear ds installed in that direction.
You can't install it either way. This DS is a custom driveshaft with a double cardan CV on one end and a regular universal on the other. The axle is pointed straight at the transfer case so the normal universal side MUST be on the axle side and the CV MUST be on the side that bolts to the transfer case.
The pre-78 T-cases were fixed yoke and no CV, so they just had a normal universal on each end of the driveshaft and could be put in any direction you want... but they came from the factory with the slip on the axle side. Having them in that direction makes sure that moisture will run out of the cavity instead of pooling inside of it(there is a hole behind the universal joint that lets air move in/out as the shaft slides).
The later models went to a slip yoke on the T-case itself with a solid driveshaft.