West Coast Performance Parts has just added a section for Grille conversions for the 05 and 06 V6 Mustangs. They have GT and Pony Package complete kit grille conversions and wiring harness kits if you already have the parts.
The link is:
http://www.westcoastperformanceparts.com/v6mufogliki.html
The link is:
http://www.westcoastperformanceparts.com/v6mufogliki.html