12-bolt gear ratio ID. Help needed!

[GAc10boy]

Just picked up a 12-bolt from 70s model squarebody to put in my '85. I'm trying to discern what gear ratio it actually has. I popped the diff cover and looked for a few numbers on the ring gear (the large one) because I've heard that both the ring and pinion gear tooth count is stamped on it. I found these numbers below in sequence right next to each other on the edge right by teeth:

6270998
10:34
GM
4
73

These were on the face of ring gear where bolt heads are:

326663N GM36

Do I have 3:40 gear ratio? Seems like an odd one but it all seems pretty fresh in there though most things are stamped with GM.

Also, this number was on the differential housing on the outside but I know all that matters is on the inside:

3896839