You loose about 200lbs with the removal of the bumpers and shockmounts. You can loose a little more if you remove the front valance and go with a motorsport update front and rear bumper. (Fiberglass)
Go with lighter alluminum wheels, loose the AC
The remainder is structural ie: larger frame rails, heavier rear end R200 instread of R190, larger fuel tank, raised rear deck to accomidate spair.
Also comfort issues ie: door pannel arm rest, carpet, springs in the bottom of your seat instead of webbing.