I believe the 6x8s are a direct fit. I don't think Ford went to the composite speakers until 2013 so you should already have the correct spacers in there. Good idea to check at Crutchfield though.
2013 GT Premium Brembo
MGW, Blow Fish, AM Hood Struts
Tinted, Borla Touring AB, ProCal Tune
Full Shelby/Kicker Audio Upgrade