Hi- this article from Patricks has stuff in it you might be intrested in. This is also in thier catalog. Very friendly people

F. Want to pinpoint engine I.D.? On the block above the end of the starter will be an initial (A-L), followed by either (2) or (3) numbers. The initial represents the month: the numbers are the day and year the block was cast. Now, then, no more guessing!

http://www.chevrolet.com.au/articles/engine_swap.htm
http://www.patricksantiquecars.com/

Good luck.
Brent