I am not sure about the GTO's but for a 65 tempest with a 326 the dipstick tube mounts on the valve cover bolt and sticks up over the valve cover. I would sort of think the setup would be the same for the 389. The pic is when we bought the car, we are in the process of redoing it now. Hope the info helps some, or maybe someone with a GTO will chime in with the right answer.
