Just a few notes from my past experience: These cars are really not heavy. When your car weighs about 3800 without you in it... thats heavy. I just got out of an 06 GTO and stepped back into a subaru and this car is waaaaay more light and agile. My car was a mild bolt on car that did 380/385 and that thing hauled ass even weighing over 400lbs with me in it! I see a lot of people are pulling their interior, taking off door pieces, changing the steering wheel and for what? 30lbs? It doesnt make that much of a difference and for the way the car is slowly getting destroyed, its not really worth it.
You can do a few things to these cars that are key and can save a good amount of weight off the drivetrain - carbon fiber driveshaft, light flywheel, pulley, rotors, and wheels/tires. These should be the main focus.