GameObject.FindGameObjectsWithTag()を使えば、同じタグ名のGameObjectを一挙に取得できる。
public GameObject[] cars; void Awake () { if (cars.Length==0) cars=GameObject.FindGameObjectsWithTag("Car"); foreach (GameObject car in cars) { //Awake時の処理 car.transform.GetComponent <Test>().dummyParam="dummy"; } } } void Start(){ foreach (GameObject car in cars) { //Start時の処理 } }