There is a difference. Not sure what the year break was, but here's a couple of pictures. The first one is the bumper off of my '74 Duster, which has a build date of 6/74. The next one is from eBay, the seller states it is also a '74 Duster bumper. As you can see, the outer bolts for the brackets do not have the same configuration. Not sure why that changed, because the rest of the bumper looks the same. My bumper was NOT a shock bumper, I don't think that started in the front until '75.