[Jeff Chambers]

I would really suggest that you pick up some good books on how an internal combustion engine works and study it well. An LS1 has a selection of heads and cams that flow circles around anything available for your 98 Cobra. Not to mention the displacement factor. If you want that kind of horsepower, its going to cost you serious $$$. The sooner you face that fact, the sooner you can concentrate your time and money on reasonable goals. You've got to set reasonable goals, otherwise you'll wind up dissatisfied with your project with no one to blame but yourself. An engine is an air pump, that's all it is. Volume in, volume out, hopefully extracting a fair amount of horsepower in between. I really, really suggest that you seek out a reputable shop in your area that can help you make the decisions. Find someone trust worthy, then trust what they say. Forget about most of what you read on this site or any other, and work directly with a shop that has a genuine interest in helping you reach your goals.