Welcome Jeff.

That is the correct Carb. for a Z16 Chevelle.The date you are showing 6A4 means it was assembled on 1966 November,4th week.Thats a 1967 models production time frame.
That would be a Service replacement for the 1965 Z16 Chevelle,not an assembly line component.
The 4557 is puzzling??
That is a 1970 Camaro-Chevelle-Nova L78/LS6 Man. Trans.Carb.suffix call out.
Does it appear to be added after the other codes,by someone later on?