Sounds like it could be your ds, did it start throwing grease?

 

Just took off all four wheels and brakes... no rocks.

Rear drive shaft is still stock but I will pull the front shaft and re-torque the pinion nut tonight.

Yeah a little, if it is the rear DS making this noise I hope it will hold up until my new one arrives!

 

I had a really similar issue but at slightly slower speeds. I checked all of the same things that you have listed here in this thread before discovering a loose balancing weight that I had bent the last time I went crawling.

Take a few seconds and wiggle your balancing weights to see if any of them are loose. My rear driver side was loose and was chirping pretty loudly against the rim as it wobbled back and forth.