I have a list of Chevy Big and Small Block head and block numbers in my wallet, for just this occasion. I passed on set of 327 "Corvette" heads at an auction a few years ago. I knew they weren't because I looked up the number. If I had a cell phone that did the internet thing I would get rid of the sheets and just look up this site:
Browse - Casting Numbers .info: engine blocks, heads, and more