OK, my univ. joints are good but the rear drive shaft rotates back and forth (guessing 1/10 of a revolution) causing a "KLUNK" in the rear. Is this normal? I don't recall this in any other vehicle.

Ya, and it's pretty much a universal thing in drive line diff setups, it's called backlash, and it lets lube
get in between the gears so they don't burn up, but there is also some slack between the spider gears
and the side gears and the splines on the axles, all of these contribute to the looseness of the drive shaft.

However too much is bad, so if you think there is a problem you might want to compare yours to another
of the same vehicle and see if it seems excessive, and if it is, have it checked or fix it yourself before you
ruin the gears, you might also have a loose pinion nut that could add to the slop

Wild

As said, what you are feeling/seeing is the backlash between the ring and pinion gears and between the sidegears and the spider gears.  The amount of rotation you have sounds completely normal.