I rebuilt the one in question.
However... I think I found the source of the problem. I finished taking it apart. The bore actually looks really good. But the plunger was scraped and pitted to heck by my previous attempts to disassemble. Just as an experiment (Oh I am such a glutton for punishment) I sweat some silver bearing solder into the pits. I will turn it on a mini-lathe to remove the excess solder and see if I can't return it to it's former glory.
If it doesn't work, now I know the secret of getting them apart, so maybe I will get me a junkyard unit and use it to make me a "good parts" version.