Freesurfer v5 -- 2

I have a 49 subjects processed using v5. 0 of freesurfer. Unfortunately, I don't have the DICOM files of those subjects anymore. I only have the .mgz files that resulted from processing the images using freesurfer (v5.0). Nevertheless, I would like to use those subjects in another study so I need to be able to reprocess them using the new version of freesurfer, without incurring any bias.