Just Wondering about 4 link setup

If you are talking a real backhalf then yes the tank has to go. The back seat and the floor also to be replaced with aluminum. There's wheel tubs, and rod ends to consider because most kits don't come with the ends. You should be shortening the rear, buying aftermarket axles and studs plus maybe even brakes. You will have to redo the brake lines at a minimum. New wheels and best of all, big fat tires!