Possible Clues:

• Classic 1966 album with the tracks 'Wouldn't It Be Nice' and 'Sloop John B'
• Beach Boys album with the hit 'Wouldn't It Be Nice' ... or things hidden in 17-, 31-, 37- and 49-Across
• 1966 album ranked #2 on Rolling Stone's '500 Greatest Albums of All Time'
• 1966 album that's #2 on Rolling Stone's all-time greatest albums list
• Beach Boys album that spawned God Only Knows