Well, while I wait for the new rear driveshaft, I decided to shim my rear diff with the ebay shim kit. All went well except for:
#1: One of the four spherical shims behind the spider gears was deeply scored. Anyone know if getting another one is even possible? Keep in mind that these shims keep the spider gears lined up with the drive gear. Any wear means a widening gap, leading to gear wear. I've upped the oil to a heavier grade, and will be drilling a larger oil hole in place of the 1/4" one there now.
I figure cutting a new shim out of shimstock and using the spider gear to shape it would probably work, but I'd still prefer to buy a new one. Likely that is near impossible.
#2 is minor: The 12 replacement nuts that lock the ring gear on interfere with the teeth. Buy 12 lockwashers before doing this mod. You also need a vernier or 1" mike, plus feeler guages, plus a bearing puller (with at least 3.5" clearance) to complete this job.
That's about it. Now for the front diff...