Exporting from FCP or Quicktime Pro will alter the duration. Neither of these programs will resample the clip, they only change the tags. An audio editor is required to actually resample the clip, then save the resampled version as a new file.
I have gone through this countless time, getting rough mixes for live concert DVDs. They send the rough mixes as an audio CD(s), and when I bring that in it’s at 44.1. I have to RESAMPLE the audio to 48. Simply exporting doesn’t change anything.
you should import the file into Sountrack Pro, then
1 Choose Process > Resample.
2 In the Resample sheet, choose a sample rate from the Sample Rate pop-up menu. In your case choose 48 kHz.
3 Click OK.