I don’t know a whole lot about the date codes, or numbers stamped on the differentials, but I do know that I need 12 bolt rear for my 70 Z28.. and I am aware of how difficult they are to find. Lol..
I came across a local listing on marketplace for a Trans Am differential out of a 1970.
This is how it read :



“ All original 1970 Trans am 12 bolt 331 posi, leaf springs, big sway bar. Ready to bolt in. Drums are turned. New brake lines. Been in dry storage since the 80's. Dusty from sitting in the body shop. Axle code is COV. Date code is April 24 1970. ”

Is that what your looking for?