I think the proper, non confusing, terms we should remember (me included) should not include the word factory. The proper terms are standard equipment, optional, GM authorized accessory and aftermarket accessory. Standard equipment is obvious, optional (RPO)is ordered and installed at the factory, accessory is purchased and installed at dealer and aftermarket, purchased and installed by the owner. This is just to be extra "anal", in the psychological meaning of the word. I see what you mean Tim, when I read the 54 brochure, it talks about "housing below wheel" to "allow" for turn signals but they are not listed in optional equipment so, as you said, they were not "available" as STD or Optional but the 54 column was designed for their own guide accessory. As Bill indicates, the "bell" housing was there as a "space saver". So to be completely boring, technically there was no turn signal mechanism available from the factory (oops) in 54 but 54 was the first year for the bell, don't know when turn signals became std/opt..55.1 or 55.2. A 55.1 and a 55.2 Brochure would tell. It's very tricky reading because they also supplied extra lights for turn signal use which makes it seem like the mechanism/switch would be STD or OPT. No mention of the switch in the brochure nder accessory or optional equipment on oldcarmanualproject. Weird marketing people back then.
