77 K10, trying to ID my rear diff. I can't find a plate on it anywhere and I want to make sure I can get a new gasket so I can change the fluid. Anybody recognize this? I'm pretty new to trucks, and don't know a whole lot yet. I Googled 12 bolt GM rear ends, but everything I've found says they weren't on a 77 K10
https://imgur.com/gallery/kFvn96T