The main differences between the '03 and '05 models (body-wise) are the front end, and the rear tail lights. By front end I mean the front bumper, fenders and the bonnet.. oh and the headlights. There's no actual 'grille' on the '05 model that you can replace.. it's attached to the front bumper. Other than the front, I guess you can mod the '03 and '05 models with the same things (including engine). I don't own a sportivo, so those that do can probably answer the other questions you have!