We have several Cobra's in our local club. One with a few bolt ons, and the stock eaton blower makes 582 RWHP.
Another with a KB, and a few other bolt ons is well over 600RWHP.
Your best bet with a Cobra is from a dead stop , the IRS holds 'em back. Both of the above cobras have a solid rear axle now...
JSchmitz, there is no difference between a Cobra and a GTO, out the door priced. (Now that the rebates have started it might help) But I know guys that have bought new Cobras for less than a GTO.