The Go Wing was a factory option on '70 and early '71 Dusters. The Gull Wing became a dealer option for later '71 - 76 Dusters. The difference is how the ends dip down. The ends of the Go Wing has a sharper bend which causes the tips to point more down while the Gull Wing has a less sharp bend. Also '70 and '71 Dusters came with the cut outs inside the trunk lid to facilitate the mounting plates. The trunk lids on Dusters after '71 have to be cut to install the mounting plates.