I've used the old Mobil 1 Truck and SUV 5w-40, Pennzoil Conventional 5w30, Havoline DS 5w30, GC, and Castrol Syntec 5w30. All the used oil analysis I've done are approximately the same. No difference worth mentioning. Heat, cold, and staandard...no difference.
DS is the lightest conventional oil regularly available. Castrol Syntec the lightest synthetic generally available. No problems with either. Mobil 1 Truck and SUV made it feel like it was full of molasses, but the used oil analysis was good. I'm using up any GC stash I had and will go to Pennzoil Conventional. I pretty much use Pennzoil Conventional in everything now.
The LS1 is a good engine, and not subject to any requirements for magic oil. Go with whatever you want.