Lightweight K member, lighter wheels, aluminum driveshaft, Steeda makes a lightweight radiator support. I know you said without altering the interior but lighter seats help. I would assume that you don't want to delete the rear seat. That is mostly it, there are some previous threads about this.
Drop 100 lbs??? Sure! As the previosuly mentioned parts would get you well on your way there. Wheels could drop you about 15 or so (also remember that depending on what size/construction of tires you go with will either help/hurt you). The K member is around 20, I believe? Radiator support would be another couple. Aluminum driveshaft is in the neighborhood of 20 lbs lighter than stock. Depending on what your goal is (driving wise...drag strip?) removing the front sway bar will drop at least another 5 or more lbs. If you have the Shaker1000, removing the sub box and amp rack in the trunk will drop over 50 lbs!
Two years ago, when I took out almost 170 lbs from the car, I dropped my times by .25 sec!!!!! I know it's accurate as I got to the track and removed all of the "stuff" after making a few passes "fully loaded" Ran some 13.3s before I took out: spare/jack oem trunk liner/mat shaker 1000 sub box/amp rack both upper and lower rear seat passenger seat set of four heavy duty rubber floor mats child safety seat Then I ran a string of 13.1s!
Well if you don't mind having a two seater there are some classy rear delete kits that look stock (so you don't alter the interior too much), also replacing some of the control arms with tubular lightweight units can help too. Finally the last thing I can think of that a lot of people often miss is your clutch and flywheel. I just bought a 15lb flywheel which is significantly lighter then the stock unit. Also some clutch manufacturers out there offer a lightweight pressure plate option which will further drop the weight. Careful though that + a one piece DS may make the car a little tricky to drive if you get the clutch material wrong.
An aluminum driveshaft, BMR K-Member, BMR A-Arms, lighweight radiator support from Steeda which allows the use of the front sway bar or the BMR which deletes the front sway bar. Free mods are remove the spare tire and jack. If you didn't care how it looked you could remove the trunk liner as well. I don't think anyone should waste their time with the rear seat delete. Once you install the delete, you only lose a couple of lbs. Not worth it unless you like the look. Correct.
I have the blow by racing radiator support that also deletes the front sway bar. It hardly weighs anything. When I bought it it was $99. Now I can't find one under $150.... whats going on here.
Depending on your application you may not want to install a lightweight radiator support. That's strictly a drag racing part that in most cases deletes the front sway bar seriously upsetting your handling ability. There has also been some criticism to the models that retain the sway bar as they apparently decrease structural rigidity up front also affecting your handling.
I agree these parts should only be used for people who are concerned with drag racing. I'm going to end up ditching my sway bar when my car goes under it's next make over and still drive it on the street. I'm just prepared for the handling to be effected.
You could spend the $8,000+ on complete Grigg's suspension setup and save something like 200lbs is it? Heh.
