Chevy 350 Small Block Chevy?

Hello. I need some help with my motor. I recently just bought a 350 sbc. For 50 bucks. It has a low-end knock. I am gonna be rebuilding it and putting it in a 1978 Chevy Malibu Wagon. But, what I am really wondering is, is the engine is has a stamp on it, and it says CMJ. Now, I saw that and I got on the internet, and it says, it's out of a 1974 cop car. It's a 4 bbl. Can anybody tell me, if this is a 4 bolt, or a 2 bolt, before I start tearing it apart? Can anyone give me some history about this engine? Is it a special kind of engine?