Disappointed magnum head flow numbers....

Horsepower on a nitrous boosted motor at the kind of power level you're talking about is primarily affected by nitrous jetting. The Magnum head has a decent exhaust side which will help accommodate the nitrous. Head flow becomes a little less critical factor when injecting torque from a bottle. I personally wouldn't spend a lot of time on a set of Magnum heads unless you just love them. if you're going to upgrade then step up. But that being said 500 horse range is definitely achievable with Magnum heads on the juice.