Link Health Bar and TNT Damage scripts together

I have a script that is attached to a car which gives is health and has a bar associated with it. I also have TNT which causes damage. I am not sure how to make the TNT subtract damage from the car health. Here is my explosion script which I found in a tutorial and changed to the way I thought would work. It has a bit to connect scripts but I am not sure the correct syntax to make it work-

enum ExplosionTypes {TNT, Nitro, Other} var explosionType : ExplosionTypes; var explosion : Transform; var damage : float; var hitPoints : float = 0; var deadReplacement : Rigidbody; var explosionFX : AudioClip; private var explodeSecs : float = 1; private var duration : float = 1; private var isTNT = false;

Function OnCollisionEnter (col : Collision){

 var contact : ContactPoint = col.contacts[0];
 var rot : Quaternion = Quaternion.FromToRotation(Vector3.up,contact.normal);
 var pos : Vector3 = contact.point;
 
 if(col.collider.gameObject.tag == "Stockcar" || col.collider.gameObject.tag == "TNT"){
    if(explosionType == ExplosionTypes.Nitro){
      Instantiate(explosion,pos,rot);
      Explode();
      audio.PlayOneShot(explosionFX);
      Destroy(gameObject);
      col.collider.SendMessage("ApplyDamage",damage,SendMessageOptions.DontRequireReceiver);
      }
    if(explosionType == ExplosionTypes.TNT){
      isTNT = true;
    }
    if(explosionType == ExplosionTypes.Other){
      Instantiate(explosion,pos,rot);
      Explode();
      audio.PlayOneShot(explosionFX);
      Destroy(gameObject);
      col.collider.SendMessage("ApplyDamage",damage,SendMessageOptions.DontRequireReceiver);
    }
    }
 

}

function Update () { var t : float = Mathf.PingPong (Time.time, duration) / duration; if(isTNT){ renderer.material.color = Color.Lerp(Color.red,Color.gray,t); } }

function Explode(){ var expl : Transform; expl = Instantiate(explosion,transform.position, transform.rotation); Destroy(gameObject); if(isTNT) isTNT = false; }

@script RequireComponent(AudioSource);

Thanks