There's not too much of a difference between the G3 coupe and sedans other than the fact that the sedan is slightly longer and has a longer wheelbase than the coupe. The sedan is also only about 50lbs heavier than the coupe. Bumper wise, only the front bumpers are interchangeable between the two. If you want to put an exhaust on a sedan, you might have to weld some extra piping to accommodate for the extra two doors.But suspension wise, there are no differences.