Where abouts are you based? Different Motorsport bodies have different reg's as to what can and can't be done with a car. Your best bet is to contact the scrutineers for any rallies that are ran in your local area. They're the ones who have the final say whether you can compete or not. They're usually pretty nice guys who will be able to break it down the basics for you. Also bear in mind that if the event your doing crosses a border you will need to check with both governing bodies that your car is legal on their event#1