Delayed update:
I moved out of Brooklyn and what d'ya know? I fixed the K.
Someone had mentioned using a perfectly sized socket to press the ring down through the splines into its seat but for the life of me, I couldn't make it work. I got real creative but now that I have a little garage, I didn't get too frustrated. Then the 'duh' moment--the ring goes in from the bottom of the U-joint side, not from the top, splined side. I'm not sure why I was convinced for months that it wouldn't work that way, but I was. Anyway, success is sweet. The K rides again and was introduced to Big Sur today. She is a much happier K these days.
Poor little girl, stuffed in there for 3,495 miles

This is more like it:

