as others have said, the trunk is all you need to dynamat. Of course, the entire car being done would be optimal if you want to avoid any potential rattle or extraneous sound from outside, however unless you're a hardcore audiophile it is unnecessary.
CelicaHobby.com is an independent Toyota Celica enthusiast website. CelicaHobby.com is not sponsored by or affiliated with Toyota Motor Sales, USA, Inc. in any way. The Toyota and Celica names and logos are trademarks owned by Toyota Motor Sales, USA, Inc.