First, the car is a 72 El Camino. It was originally a SS 350 4spd if that matters. When I purchased it a few years ago, I was told it had a Pontiac 12 bolt 3.42 gear in it. That's about as much as I know aside from the following pictures.
It appears to have a C-Clip eliminator kit installed. Possibly bigger axles.
To keep you from having to count I believe they are 31 spline. 1.2326" diameter.
Years ago I bought a disk brake kit and I'm trying to install it. I believe the C-Clip eliminator kit is messing me up. That's another story, I'm just trying to confirm the ID of the rear end and modifications so I can figure out the next step in the rebuild.
I'm not sure if there are other numbers or information you need. Please let me know.