Chevy code numbers

I lost a link to a site that gave GM numbers of engines and transmission's late 60's early 70's. Does anyone know of a site that I can trace the numbers down?

Thanks Richard

I found it if anybody is interested.

http://www.nastyz28.com/chevy-transm...tification.php

http://www.nastyz28.com/sbchevy/sblock.php

http://www.cehighperformance.com/new_page_3.htm