Hey @Uncle Gump, tried what you said but didn't notice any difference.
However, the symptom has changed to "pretty quiet while its sitting there, loud as hell when I touch the clutch pedal."
While addressing some leaks and rust stuff I tore out all the old carpet and took the rubber boot off the shifter in the cab, and then it became extremely clear the noise is coming precisely from the bell housing, so I figure it's got to be a bearing.
I've almost assembled all my tools to put in a clutch kit I got, so I'll update with how that goes.
I'm sure it's gonna confuse the hell out of me though so I'll probably make a thread of the process so I can post pics and ask questions.
To me that sounds like one of the shields on the catalytic converter rattling, though you say pushing in the clutch changes the sound, which that part I don't have an answer for...
I actually had the solenoid (bendix) come loose on my '94 4.0L starter one time and the starter pinion gear would "fall" into the flywheel while accelerating or while pointed uphill. The noise was very different from that (more like a simple clicking or tapping sound as the pinion bounced off from hitting the flywheel).
It often can be hard to tell sounds not recorded with good quality microphones or audio setup (especially after it going up on Youtube), though to me that still does not sound internal to the transmission (more like a piece of sheet metal rattling rather than a bearing).