Another thing are all the brackets in the engin compartment for the air canister and other junk. buy a drill to remove them (spot weld drill?). Depending which year you have some of the bumper mountint points were much beefer and an area to look at removing/lightning. Ron was right about the dash the 280s were a lot heaver than the 240s if possible pull it and gut it they had a lot more material and braces inside and if the dash is out remove some of the mounting brackets for the ac and other interior parts you are removing (drill again). And like everyone said the undercoating. When we built our IT 240 we weighed the undercoating from the floor pans and interior got 12lbs out.