pixel in unit in unity3d and have a full screen texture

this was my code after a long research ,,,,but unity released a new version...!

 var NewObjectWidth : float ;
 var OldObjectWidth : float ;
 var NewObjectHeight : float ;
 var OldObjectHeight : float ;
 function Start ()
 {
     OldObjectWidth = this.transform.localScale.x ;
     OldObjectHeight = this.transform.localScale.y ;
     //NewObjectWidth = (OldObjectWidth /1366) * Screen.width ;
     //NewObjectHeight = (OldObjectHeight/768) *  Screen.height ;
     //print (OldObjectWidth);
     NewObjectWidth = OldObjectWidth * 768 / 1368 * Screen.width / Screen.height;
     this.transform.localScale.x = NewObjectWidth ;
     //this.transform.localScale.y = NewObjectHeight ;    
     //print (NewObjectWidth);
 }
 function Update ()
 {
     
 }

and this was the camera code

 var ScreenHeight: int ;
 var SW : int ;
 
 
  
 function Start ()
 {
 SW = Screen.width ;
 ScreenHeight = Screen.height ;
 camera.orthographicSize = ScreenHeight/2 ;
 }
 
 function Update ()
 {
     
 }
 

but now everything is changed i want my background fill the screen and then other objects .... would anyone please help me im so confused now the scale depends on pixel to unit parameter , so how can change the camera...................