That this has been 'debunked' is old news, the Mustang does not weigh nearly as much as those 'early estimates' indicate. In fact, those early estimates weren't actually estimates at all, they were a joke with Ford going for a bit of humor at GM's expense. Think about it. Does about 3750lb for a V6 coupe and roughly 3875lb for a V8 coupe sound familiar to any of you guys? Those numbers are basically spot on what the V6 Camaro and V8 Camaro weighh respectively! Ford was taking a light-hearted jab at their cross town rival GM by posting Camaro curb weights for the Mustang basically saying that the Camaro is a little portly without actually saying it.
Here is a link to Ford's later and more accurate releases of the 2011 GT's curb weight.
http://media.ford.com/images/10031/2...g_GT_Specs.pdf
The estimate for the GT is 3603lb for a 6m car. Of course, the V6 weighs less than the GT does.