Will be most curious to see if you get a response from the MB museum re the 230 SL. It has been on display a long while. It might even have been in the old museum.
I got an answer this morning to that question and some other questions... I spoke with Andreas Hosch, "Product Management Classic Spare Parts".
In re: the chrome arch. There was no answer. I view this as an answer.
I asked about if a M116 motor was ever considered in the 113. They said they built a prototype, but didn't elaborate. I suspect he is mistaking an M116-powered car with the well-known 6.3 car.
He referred any questions I have about pre-merger AMG to AMG-classic. I asked about whether AMG had ever considered racing the 113, as it was contemporary to their time, and if so, if there are any details/drawings/literature about such a car. I await a response from AMG.
I asked about the Talbot mirror shown in factory videos of the 113 upon its debut and whether that was going to be considered an option. He has no information to that.
I asked about the yellow headlight covers one sees on eBay, Authentic Classics, etc and if those are genuine, as they have the same part number as the clear ones. He said all French market cars had other reflectors, yellow chrome (?), yellow lights. All the lenses are the same for all across all of Europe, and no special lenses were made from the factory for the French cars.
Some time ago I posted a thread about plaid fabrics in the 113 and how they were never offered, unlike the SLs before and since. I asked if the factory had considered this as an option. He said no.
Altogether, the car in the museum is still a mystery.