It all depends on the setup. I've put some stock block motors deep into the 11's. If you are going to build stay away from ebay parts and DO NOT run a block guard.
whats your reasoning for not running a block guard? it cant hurt i think. NOTE: installation of a block guard should be done by a professional. the bore will need too be honed too assure a perfect cylinder. Engine Lab of Tampa does them. the did ICS/ICC's block guard in his LS