1969 Camaro big block SS, 10C car. Diff is 06-12.What could be the earliest stamp on the diff that would be correct for the car. How many months could the diff stamp be off of the build date of the car. There is a casting date on the diff as well. When was the diff stamped during assembly? Trying to find out if a 6 month gap between the trim tag and the stamp on the diff is too much.