If you don't mind a self rec, you could check out my Trek Reverse Bang from a couple of years ago: A Rose By Any Other Name (http://archiveofourown.org/works/206094). It's a sequel to a Kirk/McCoy fic I wrote, A Cat May Look At a King (http://archiveofourown.org/works/206173), but I think it can stand alone.

Also, I have a few Pinboard bookmarks for Kirk/McCoy/Gaila here (https://pinboard.in/u:SailAweigh/t:Kirk%252FMcCoy%252FGaila).