The Technical Manual has Month of Production information.
Go to Data Cards and Codes, then Production Statistics, then look in the column for your model, look down to where the last 6 digits of your VIN belong to find the Month and Year of production.
Don't be surprised if the Production Year is not the same as the Model Year of your car. Model Years started as early as August...a car built in October 1968 could have been sold as a 1969 model car.
Richard M, NYC