ORIGINAL: Jeremiah 29:11
You can count on performance packages but I dont think they will make it lighter. The only way to make it lighter is to come up with a new platform that is not based on heavier sedans.
About the only thing you can do is replace hood, trunk, doors, with carbon fiber but that would be expensive.
I think the size is most of the problem. Here is what I've noticed about the Mustang and the Challenger and the 06 GTO:
Ford Mustang GT500
the length is 187.6 inches
the width is 74.0 inches
the height is 55.7 inches
the wheelbase is 107 inches
weight 3920lbs
Dodge Challenger SRT-8
the length is 197.7 inches
the width is 75.7 inches
the height is 57 inches
the wheelbase is 116 inches
weight 4140lbs
06 GTO
the length is 189.8 inches
the width is 72.5 inches
the height is 54.9 inches
the wheelbase is 109.8 inches
weight 3725 lbs.
The Challenger is practically a class bigger than either the Mustang or GTO, his explains why it weighs so much. The original GTO was supposed to be in a class with the Charger, yet this current Challenger which is using a large car platform is larger than it. Cutting the wheelbase did very little to cut back on the size as it is still very similar to the 300. Basically, its a Charger that has been styled after the Challenger and named the Challenger.