Help identifying shifter (pictures)

I agree, it looks like a UUC (which is what I have). It should bolt right in without anything else, although it would be very wise to install some Creative Steel shifter rail bushings while you're in there.

I'm curious what that knob is on there, and if it's threaded on or what? Do you have the part in hand, or is this something you're considering buying (and just trying to do some research before you make an offer)?

Assuming it snaps on like the stock knob, as you're trying to pull the knob off, simultaneously try to twist it around the shift lever. I've found that pops it loose.