In mid year, not sure when, the door frames were changed. It affects the window regulator. An early regulator will not fit the later door frames, but the later regulators will work in the early door frames. I found this out when I sold a regulator that was going into a 71. He had the later style doors and the regulator was restricted for full travel from the gear hitting the frame. Neither of us knew at the time about the changeover. He was able to trim the 70 regulator gear down and then it worked fine. Hope this helps.