It's most likely a cast iron OD box, it has the newer side cover and large bearing retainer, one of my friends has one in his shop I was checking out- came out of a 74-75 318 Dart as far as he knows, I think they went to aluminum cases around 76 so the later A bodys and F bodys had them. All the SB A body 833's I've seen use the smaller 4.30" bearing retainer.

He got burned too cause it was represented as a 3.09 1st, 1-1 4th 833, right now it serves as a door stop and wheel chock.