I agree with lxarlo 100%. I would think that NOS is more harmful to your vehicle than a SC. I've heard horror stories about NOS, like the top of engines blowing through the roof of the vehicle and such. I think a pulley is a great bolt on to have; I plan to get one next year.
You can still find a used SVT Cobra under 10,000 miles for about $29,000 to $30,000 dollars. Be patient and look carefully. You may have to travel as I did.
Here's a Whipple Supercharged Cobra for $42,000 dollars!!!!
Used Car Listings - MSN Autos