casting numbers for chevy engines are at

http://www.mortec.com/castnum.htm

to get specific year info for a particular casting, you have to look for the letter code on the block pad just in front of the passenger side head. There is a code that contains digits and either one, two, or three letters. The letters can be decoded to tell what the original engine was; the carb type, the transmission in the car, etc.

mike in tucson