I just thought I'd give everyone an update. Well it's not really an update since I still have not determined where the noise is coming from.
To better describe the sound, it sounds like someone is scraping a knife or using a plane back and forth against the bell housing 3 times. The first scrape is pronounced and the third scrape is barely discernible. Or if anyone has machine shop experience it sounds like a shaper.
It's killing me because as long as I don't jump on/off the gas it makes no noise and runs beautifully. I also pulled my 8K# TT this weekend and didn't get any noise driving normally (e.g. not jumping on/off the throttle). My plan is to keep driving it until it either gets worse enough to clearly diagnose or it fails. With my luck it will likely fail when I'm travelling later this year with the camper in tow in some remote area, temps in the upper 90's and the truck packed with cranky kids.
As for the other noise inside the cabin, have not diagnosed that either, just getting used to it.