1970 used the thicker chrome edge vents, and the passenger vent had a push/pull lever to open & close a flapper door to regulate the air flow. Some of the thick edged vents may have found their way onto early 71 cars, but for the rest of 71 the thin edge vents were used. The passenger vent still had the lever in 71 also, maybe that faded out at the end of the year?. 72-74 also had the thin edges, but the lever in the passenger vent went away altogether. The plastic housings themselves are E-body only and all the same from 70-74. 71-74 B-Bodies used the same thin edged vents as 71-74 E-Body, and make good donors (cheaper to find) if needed.