steering column pros - HELP!

[oem4me]

What the %#$@ is that rattle?? Hey guys, hoping those among you with extensive steering column experience can help me figure how to stop the annoying rattle within (I think) my steering wheel/directional hub of my 66 C20 3spd auto. Actually, the rattle may not even originate there, but that's close to where I hear it.
Last weekend I took up a bit of in-and-out shifter linkage slop (TH400) by moving the upper column adjusting ring screw nearly the full length of its helical slot. That did tighten things a bit, but something still sounds sloppy in there.
The shifter detents all seem positive and the indicator lines up well enough with where it should, but I do notice the shifter arm still has quite a bit of side-to-side motion.
The upper bearing is fine and the wheel has no excess play.
Can any of you tell me simply what the key wear points are and what to look for so I can eliminate whatever has slop in it.
The truck as a whole is fairly tight, so this dang in-cab noise is driving me nuts. Anyone?
Thanks ahead of time.