Welcome to the site. I have a '57 GMC as well and researching them has brought out a ton of info on all of the little differences between the Chevrolet Task Force trucks and the GMC Blue Chip trucks. Good thing is, it looks like you have all of the chrome trim pieces for the font end. If you are patient you can find some good grills out there on ebay if you cannot straighten yours out. They can be pricey.
Here is a GMC brochure which talks about those Road Shock Dampers.
55-59 GMC Brochure Look on the bottom left of the second page. They were a dealer add on. Not too many of them still out there. It's essentially just a big spring with a lead weight inside the cylinder. As to if they actually do what they say, is up to anyones guess.
