I've searched but didn't unearth a good answer. The Stant "vintage" catalog lists 10559 as being the correct cap for '71-72 1010 and 1110 fender locations as well as 1210 and 1310 trucks for the 1971 model year only. They curiously have no listing for any other D-series year. Rock Auto concurs, apparently having taken their cues directly from the Stant catalog. This is the wider and skinny "saucer" shaped cap, not the smaller, thicker cap that is for the cab fill location and also shared with the Scout II. First obvious question that arises is, what the heck could be different about the fender fill location from 1971 and either earlier or later years of D-series 1210 trucks? This seems like an incorrect or incomplete information situation on the part of the manufacturer. Then the next obvious question, has anyone used a 10559 on a 1973 1210 fender fill? I don't want to buy it to try it. I want to know that it will work beforehand. Thank you.