We sell the US and Dynacorn made trunk lids at Camaro Specialties. The primary difference on the lids is the detail on the underside. The welds are more factory like, and I think there may be some other little thing that I am unsure of that make them stand out.
As far are sheet metal producers, there are only two primary sources that we get after market sheet metal from. That is Golden Legion and Dynacorn (DII). There is somebody else who has been producing the early 67 convertible 1/4 panels with the hour glass stamping in the door jam, and that is about it. Goodmark is a retailer such as Rick's, Camaro Specialties, as well as many other shops out there selling the same stuff.
If you have any trouble getting a trunk lid to fit properly, let me know and i can give you a couple tips as I have seen quite a few different scenarios.