1968 Dart GTS grill center
I haven't had a spare in a LONG time, but that one cost me $2. and change back in the 1990s at a local wrecking yard. A guy who was an editor at Petersen Pub back in the 1980s had bought three when Chrysler was blowing them out at $3.+. Yeah, those days are over.
As for what I have heard on what cars got them. It was early GTS cars only. I don't know what constitutes early, but my 8/28/67 SPD GTS has one, BUT the grille and the rest of the front end was replaced in 1970 (2nd owner accident).