I am not sure about an LS1, but you should think about a header that dumps at the rear, as opposed to block huggers. The block huggers on my 350 only have about 2" clearance from the snout on the steering rack. For now I am using a carter carb, and Vertex mag. They are pretty tall, and don't clear the hood, but if the fuel injection and dist are stock, you should have room under the hood.
Joe