Bumpers first. The short answer is yes, they will interchange. The long answer is convertible front bumpers stick out more because of the mounts, and have weights in the ends. The coupe front bumpers fit snuggly and look cleaner. They also have slightly different plastic grills above them. The real early coupe rear bumpers have extra brackets along the sides. All of the coupe doors are the same. All of the convertible doors are the same. The 81 doors use a different interior lock. They also have a different trunk lock. Early coupe door panels don't have interior lights. Coupes had white and black visors. Converts had ones to match the rest of the interior. The panels behind the seats have a sharp edge at the top on coupes, and are rounded on converts. There are other differences, but they will be covered next semester.