I've recently finished the above book, "Pre-Code Hollywood: Sex, Immorality, And Insurrection In American Cinema, 1930-1934," by Thomas Doherty (Columbia University Press, 1999), an informative volume on that period of American film history. (The cover is a famed "thou shalt not" poster of the period, more or less detailing the things that were forbidden under the Code but not really enforced until mid-1934.) It may be a bit too scholarly written for some tastes, but it not only covers feature narrative films, but newsreels and documentaries too, giving the reader a real sense of movie fare during that volatile period. All in all, it's a fine complement to Mick La Salle's books on that era, "Complicated Women" and "Dangerous Men."
There is a Carole Lombard reference in Doherty's book...though you won't find it by skimming through the index, where for some reason her name isn't listed. It's late in the book, in a section on Joseph Breen, head of the Production Code Administration -- arbiter of movie content for nearly two decades.
In August 1935, Paramount apparently wanted to reissue "Bolero," a film released in early 1934 before the Code was strictly enforced. We know that a few theaters, mainly in large cities, specialized in reissues or "subsequent runs" (http://community.livejournal.com/carole_and_co/95185.html), and perhaps this was the market Paramount was eyeing.
According to Doherty, Breen wrote Paramount's John Hammel that for it to win approval for a reissue, it must "re-edit the scene between George Raft and Carole Lombard so as definitely to remove present inference that they spent the night together" and "eliminate views of dancer wiggling her posterior at audience" (since the dancer isn't identified, it may not be Lombard).
I haven't seen "Bolero" in a long time, so I don't know whether those cuts were made, whether the version available to us now is the edited or original one, or even if the reissue ever took place.
On the other hand, if one did occur, I tend to doubt this scene, in which Lombard's character dances in her underwear and stockings to audition for Raft, got past Breen, as images of lingerie were now verboten on screen: