1968 Hemi Carburetor Dates/Build date

Generally speaking, did the "range" of Hemi carburetor dates used change over the years based on the build dates of the car? For instance, what would be the judging accepted date range of carburetors for a January 68 build car be and what would be the judging accepted date range for a January 1970 built car be? I know inventory control was not consistent at the various plants, but generally speaking....

Also, is it common to have the carburetor months match or more common not to match?

Thanks.