For a high power LS engine, features that would be beneficial include a large displacement, cast-iron block or aluminum block for light weight, and forged pistons which can deliver more power. Some manufacturers offer both heavy-duty and high-performance LS engines.
Testing the limits of your camshafts is key to any build, but also consider redline timing and fuel injection. While these are not always necessary for LS engines, they will help produce increased power and make sure the engine runs smoothly.