307 or 327?

[stoutguinness]

Ok, so I have done work on 350's and 454 fords but I have never done a complete rebuild or anything like that. So by no means am I an engine guru. I just picked up a 68 Chevy C10 long bed and the engine is definitely smaller than a 350. I cannot figure out if this thing is a 307 or a 327. I've talked to a few guys around town who know a lot about Chevy's but one will say 307 and the other will say 327. I spent a lot of time yesterday trying to find the casting number or any number that will identify this thing and can't find anything. Is there a way to figure this out without ripping the engine out? I've read a lot of post saying where to look but have not had any luck.
It's obvious that the guy who had it before me has done some different stuff to it, so I don't really know what I'm working with. My goal is to have this be a daily driver so I don't have the luxury of having a machinist tear it apart to tell me all about it haha.

Here's a pic if it helps.