2010 only body changed hp went up about 10 on the gt.. v6 didnt change.. 2011 was the big changes. new engines 5.0 for the gt and 3.7 for the v6. the v6 mustang is the first v6 with over 300hp and 31mpg. btw the 2011 v6 is as fast as the 2010 gt. but in the long run the gt's torque takes the lead. for 2011 the suspension was fully reworked.. check motortrends site.. a mustang gt with 3.73 gears($400 option form ford) kept up with an m3 around a test track only to lose by .09 of a second. so its an amazing handler. and interior quality went up in 2010 and more in 2011. with the edition of folding rear headrests. and a sport mode on the traction control..and other small things that are unnoticable. 2012 nothing has changed.. but there are rumors that for 2013 the gt is getting direct injection and a few minor revisions to get 440hp(which, in real dynos, it already makes but ford deneys) so the 2013 should be making about 470ish hp on the dyno..