Did a 1976 Chevrolet c-20 van have 2 or 4 bolt main?

The 1976 Chevrolet C-20 van could have had either a 2-bolt or 4-bolt main engine block, depending on the engine option selected. There's no single answer. The smaller engines were more likely to have a 2-bolt main, while larger, more powerful engines typically had a 4-bolt main. You'd need to know the specific engine (e.g., 350 small-block, 400 small-block, 454 big-block) to know for sure.