Julian Date Codes vs Cowl Tag Build Dates

[SS69chevelle]

Guys, FWIW, I track 69 Chevelle data and have this same issue and have tried many times to tie the build weeks to a calendar with no success. As far as the build month and weeks I have several that run beyond the monthly reported VINs for an assembly plant, example would be the Baltimore assembly plant in June 1969, many of the early June VINs have 05D build month and week. This did not occur at all the assembly plants and not for all the months but there are several where it runs over.
For my 1969 chevelle, the NCRS production date is the same as the transfer date that is found on the Manufacturers Certificate of Origin.