Juanita Hall, who had played Bloody Mary in the original Broadway production, obviously sang her own songs onstage, but was dubbed in the film version at the request of composer Richard Rodgers. Rodgers and musical director Alfred Newman brought in Muriel Smith (who had played Bloody Mary in London).
The film of South Pacific ran for just under 4 years and 6 months at the Dominion Theatre in London. It opened on April 21st, 1958 and closed on September 30th, 1962, for an unbroken, record run that will probably never be equaled.
This is the only theatrical film adaptation of a Richard Rodgers and Oscar Hammerstein II stage show to have all the songs intact, with the addition of the song "My Girl Back Home," which was cut from the play before it opened.
Dating back to the development of the stage musical, Richard Rodgers and Oscar Hammerstein II were pressured to eliminate the song "You've Got To Be Carefully Taught", but they resisted. The movie was greeted with objections and even boycotts in certain parts of the country specifically because of the song.
France Nuyen had not yet learned English when playing the role of "Liat". Fortunately, she was able to converse in her native language (French) with co-star Rossano Brazzi, who spoke French as well as his native Italian.