I looked up the GM part number for the 2.73 12 bolt ring and pinion gears.
There are two part numbers in Group 5.529
3875267 shows for 65-68 Pass and 67-68 Camaro.
3961435 shows for all 1969. Those gears are 3869788 and 3869785
This guy on eBay has a set of 3875267 NOS. You must click "See full item description"
https://www.ebay.com/itm/NOS-1970-Z2...YAAOxyu0BRfJHz