The 05 GT no doubt is the faster ride. 5 hp more that the mach 1 has will not beat out the new tech of the 05:
http://www.carsdirect.com/research/compareresults?acodes=USB50FOC051C0,USB40FOC051F0
Here are the dyno results of a Stock 05 GT vs a Stock 04 Mach 1. Blue graph is the 05 Gt, the red is the 04 Mach 1:
http://forums.modularpowerhouse.com/attachment.php?attachmentid=3997&stc=1
Also, here is a link to the thread where I got this information:
http://forums.modularpowerhouse.com/showthread.php?t=8993&page=1&pp=15
http://www.carsdirect.com/research/compareresults?acodes=USB50FOC051C0,USB40FOC051F0
Here are the dyno results of a Stock 05 GT vs a Stock 04 Mach 1. Blue graph is the 05 Gt, the red is the 04 Mach 1:
http://forums.modularpowerhouse.com/attachment.php?attachmentid=3997&stc=1
Also, here is a link to the thread where I got this information:
http://forums.modularpowerhouse.com/showthread.php?t=8993&page=1&pp=15