So I swapped the fluid, and everything looked fine, no shavings, burnt smell, metal chunks, etc.
But, after I took it for a test-drive, I pulled up on the shifter, and the noise went away! So I think the culprit is my shift selector hitting my guibo. When I was under there, I did notice a small amount of goo on the shift selector rod.
I think what happened is when I swapped the bushings for the diff hanger, the old ones were completely blown out and the center of the bushing was almost sitting on the metal outer ring. So when I swapped out for new, I ended up raising the diff slightly, causing the guibo to contact the shift selector rod.
Anyway, that's my theory. Next question is how do I go about lowering the diff/driveshaft so that the guibo and shift selector rod play nice?