Craig- The weight difference should be a lot more than 500-600 lbs. It should be closer to 1000 lbs difference since Vipers weigh in at around 3400 lbs.
Where Vipers, Vettes, etc....usually get Cobra's is off the starting line. This is mostly due to their superior tires (I think Vipers have sticky, low profile 345's on the back). We Cobra guys have to keep from spinning our tires too much when taking off. In my experience, I usually end up overtaking them by the time I'm thru 2nd gear.
Stick some BFG drag radials, or some sticky AVONS on the back, and you will be good to go!
