Like olerodder said the new mounts are not required but they do make a difference. I ordered an eibach pro-kit with the 2008-2010 struts and the fit is much better. Wish I could find the pic of the mounts side by side. I've driven some cars with and some without the mounts. The ride seemed better with the gt500 mounts. By better I mean less noise.
A question that drove me crazy was which springs to use. 2008-2010 or 2011-2014 some state they go from 2008-2014. Ford springs are 2008-2014. According to a few mechanics I spoke with the springs are the same except for the rate and drop. I can confirm that any springs from 2008-2014 will work.
Edit: I have a 2012 GT
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