How do I ID a 340?

So far I've only had slant 6's but I found a pretty cheap car and the guy says it's a 340. I went and looked at it and it idles nice but I have no idea if it's an actual 340 or not. I brought a paper with the v8 casting numbers on it but I couldn't really see anything with the exhaust manifolds in the way. Does anyone have a picture I can reference? I'm not sure if I need to get under the car or if you can see it from the top or what. Also if I can't see the casting number, is there any other way to ID the motor while it's in the car? Thanks!