what car are you driving thats 2500lbs?? Hell a civic weighs 2400lbs... Unless you drive real lightened drag-only cars, 2500lbs is really really light. I'd say 3000lbs is a good weight to try to get your v8 sports car to. Even the fiberglass bodied 2 seater vette's are over 3000lbs. The only sporty car that I can think of thats under 2500lbs from the factory is the Saab Sonnett... I always wanted to put a 9" and a 289 in one of those. Someday...
I'm not saying a 2500lb v8 car isn't possible, but its rare and difficult to do. If you do have one, congrats! it must be fun as hell to drive. Maybe a GT40 or Cobra replica w/ a 289/302?