Just put together my forged, balanced and blueprinted LS1. Total Engine Concepts did the machine work but didn't give me an oil recommendation other than to use a 10W30 oil.
Order some Brad Penn 30wt break-in oil on amazon. It is Loaded with all of the good stuff. That would be my recommendation. I know a few people who do mods and use Brad Penn 30wt exclusively never heard of one oil related mishap.