I think Fender supply 34" scale strings on all their new Mustangs, at least the ones that I've seen.
I have 2 Mustangs, one has through body stringing and the other has a regular BBOT style bridge. I've replaced the stings on both basses with 34" rounds (I'm not really a flats guy) and have not had any issues even when refitting the strings after taking them off to clean the fretboard. You do, however, have the thicker, non-tapered part of the E string wrapped around the machine head post so when fitting them new, so when cutting the strings allow for no more than 2 to 3 wraps around the post. I've been doing it for around 3 years without any problems.