I disagree with any posts that assume "anything is possible" or "Friday built"
The manufacturers would have a lot of liability with any "Johnny cash" special they let out the door.
The way it works is your owner's manual is a contract. They write the owners manual for liability reasons because there are warnings and instructions.
Equipment that is not in the owner's manual must by federal law (as early as the 1940s) be documented. A manufacture must issue the dealer a TSB outlining the exception or change explaining what, why, where, and how to service whatever was not included in the owner's manual. ( good example is the rally dashes put in 68 valiants by the factory)
The federal law gives manufacturers small windows to make changes without being responsible to recall and fit previously made cars with the new equipment. Calendar year is one and the other is mid year. (Mid year to manufacturing time table which is usually march or April). However, changes or add ons in these time frames must be documented.
This is why half year cars are only half year cars if specified by the factory. ( example is the 69 1/2 six pack roadrunners)
When they built these cars, the paperwork was done and it wasn't a random thing. Dealer service places recieved TSBs and dealers recieved addendum literature and training on how to identify, sell, and service the new or added equipment. The cars themselves were clearly marked to differentiate them.
Theories of "transitions" or randomly "thrown in" features is pure bullshit because big brother would not let manufacturers be so loose and it would be a huge liability in a federal court room to be so random. Liability from the consumer, the service technician and even from the assembly line worker.
Every year a new owners manual, service manual, and TSBs come with training and paperwork for that year and what will be available to be in compliance with federal law enforced through the NHTSA.
No documentation then it's bullshit, the stinky kind too...... and illegal.