THanks, Transman,
I would say that in general, the transmission works OK except for a slip / RPM flare on the 2-3 shift. After finding the trans cooler leak, I changed the fluid, but somehow didn't find the drain plug on the converter so it didn't get drained. This material was what came out after running the initial flush for a bit:
2013-12-28_Trans_Pan-01 by clair_davis, on Flickr
2013-12-28_Trans_Pan-02 by clair_davis, on Flickr
2013-12-28_Trans_Pan-03 by clair_davis, on Flickr

Not knowing how much junk could be elsewhere in the trans, or even what all the junk was, I don't have a feel for how much damage could have been done to the converter before I got the car, or what might happen if I can't get everything out of the converter when flushing. I don't have a loose input shaft, but I might be able to pull one from the trans during the R&R.

From a logistics standpoint, I'm rebuilding a '77 model from a New Yorker that seemed to drive and shift fine on the short trip home, and I'm going to stash the numbers-matching 727 in the garage. The goal is to get the 77 model rebuilt over the next week or two, and install the rebuilt trans the same day I pull the original trans. If the original converter has problems cleaning up, I'm down for a few days while another converter ships from somewhere.

I'll take a look at the FSM to see if the stator check is something I can do at home.

Thanks for the guidance!

Clair