These are a set of the original RuffStuff Specialties "canoe style" trailing arms. 62" long and tig welded. Here is Dan Fredrickson's post about them from when they were released.
https://nc4x4.com/forum/threads/trailing-arms.157245/#post-1302890
They have been mocked up on a project truck, but never driven on. They currently have surface rust as shown in the mounted image.