The Deville seats are buckets. They have two tracks per seat. Your bench only has the outboard tracks. You are missing the brackets welded to the floorwell that the inboard tracks bolt onto. So yeah, this is not much different than the situation that you would encounter with any buckets, including the "correct" G-body buckets. However, the spacing between inboard and outboard tracks can be different, for example, in 3rd Gen F-bodies the spacing is narrower. You can get the brackets to weld in, but they are shaped to fit the floorwell shape exactly where G-body track spacing expects them. If the track spacing is different, or you just don't want to weld the brackets in, some kind of adaptation will be required.