I thought on Pontiac Motors on the passanger sie of the block they has the Cubic Inch cast into the block? Above where the fuel pump is on a SBC...
I done some quick research and here is a list of sites...
I still did not find your numbers..so are you sure you are looking in the proper location for the numbers?
http://www.teufert.net/identify/identify.htm
http://www.pontiacstreetperformance....p/blockID.html
http://www.yearone.com/updatedsingle...ontengid1.html
http://www.pontiacpower.net/castnum01.html