Canon 5D Mark III SMPTE Time Code
I am not quite sure that people usually bother to sync the audio these days.
A lot of the time I have noticed that the small TV companies that use 5ds and 7ds, just free run the cameras and 'jam synch' in Premiere from a commonly recorded 'clap'.
True professional video cameras have full synching and clocking facilities.
The 5D3 has no SMPTE generator as far as I know, but you should be able to record code on the audio track, generated with an external master device, that feeds all the other devices.