If I am not mistaken the metal retaining clips were only on certain trucks regardless of the year. They used metal to hold the rubber to the door on trucks used in very cold weather where the water might get down between the seal and where it sits and then freeze. When the frozen shut doors were "pried" open it pulled off the rubber. That is why they decided to use the metal strips. Might be an old wives tale but it sounds valid and anyone who has had a frozen door can attest to the logic of using the clips.
