While we usually say Mercon/Dextron III as it was spec when the car was built, recently Ford issued a TSB to say that Mercon V is the new tranny fluid for all its automatic transmissions. So, yes, if that is what you have, use it.
Read this.
http://www.contour.org/ubbthreads/showflat.php?Cat=&Board=tranny&Number=1280884&Forum=tranny&Words=mercon%20v&Match=Entire%20Phrase&Searchpage=0&Limit=25&Old=3months&Main=1279489&Search=true#Post1280884
