The key is dynamic compression ratio not the static one. Going to a more conservative cam that closes the intake earlier raises the dynamic compression. Numbers on LS1s used on the street are typically under 8.8:1. Even then, you are skirting the limits of pump gas. Using a racing gas avoids that issue.
http://www.kb-silvolite.com/calc.php?action=comp
http://www.wallaceracing.com/dynamic-cr.php