Did you buy it new? If you take the rear seat out, on the underside (in the springs) you will see the broadcast Sheet. It will have your VIN and all the options that came on your car. What factory engine do you have. With the Sunroof, it is rare
Is it difficult to remove the rear seat (I've never done something like that? I'd like to find the broadcast sheet of my car, but my Valiant got a new interior. So I think the sheet is gone anyway. But still, if it's easy, I'll try it.