I speculated in my April 22, 2013 post that Paul's real last name might be Black, so I started thinking about songs around the year 1966 that had the word "black" in them. Of course, The Rolling Stones released the song Paint It Black in 1966--recorded March 6-9, 1966 and released May 7, 1966 in the US and May 13, 1966 in the UK, so I checked for backmasking in the song and I found some.
The song is on Youtube at: http://www.youtube.com/watch?fPVUa29kHu8 .
Beginning about 2:47 in the reversed song, you can here Jagger sing something about "out."
At 3:08-3:11, you can hear: "He was from us . . . but he's out."
If you remember the Christmas Time Is Here Again song from the Beatles' 1967 Christmas fan club record--which I believe chronicled the selection of our Paul's replacement--Ringo sings, "O-U-T spells OUT" several times in the song.
Was Mr. Black on his way out in early 1966?