To find the year, you'll need to:
* Check the vehicle's documentation: The best way is to find the vehicle's build sheet or owner's manual.
* Look for other casting numbers: There might be other numbers stamped on the differential housing or other components that can help narrow down the year.
* Use online resources: Websites and forums dedicated to GM vehicles might have databases or discussions that could help identify the rear end based on the casting number. However, this requires a thorough search.
In short, the information provided is insufficient to pinpoint the year. More information is needed.