For at least Flint and Tonawanda, the CE stamp does not include the month that the block was machined. Following CE, the number denotes the last digit of the model year. Each engine assembly plant was assigned a block of 5-digit serial numbers, which followed the model year digit. When the last number was reached, an additional letter was added after the model year number for a second run, for example CE9A, then that plant's block of serial numbers followed. If a third run was required, it increments to CE9B (for example), and so on.
More here:
http://www.camaros.org/engine.shtml#ReplacementEngines
and if anyone's interested, a thread which I started on the same subject:
http://www.camaros.org/forum/index.php?topic=12873.0