Hi Pete and All: The "cast in" part number is the number of the casting only. Adding the attachment studs makes it a different part number-----an assembly. I have to admit I am a bit puzzled by the name they applied to them though----Lamp, Quarter panel tail, stop, and turn signal. I would think "housing" would have been more appropriate. Since the 1960 908, 909 are kind of near the end of that "batch" of part numbers, it is possible there were no more 1960 *** numbers left when the time came to assign a number to the housing assembly. Only seeing the engineering drawings could answer your question absolutely, however. Does this help? Hope so. 300ly, Gil C. [Non-text portions of this message have been removed]