The Vortec heads will make a TON more torque than anything else available from the factory. They flow considerably more at all valve lifts. That means you can pack more air/fuel into the cylinders for a given cam duration/lift which means you can make more torque on a short duration cam. Using the short cam really holds back your engine because the valves are open for such a short time and it can't pull enough air into the cylinders. Often times, long duration/high lift cams (what we consider high revving cams) make more torque than short duration cams.