I have a GM846 cam and decently ported heads with 1.6" roller rockers and I'm north of 400 horses at the crank.
Are you talking crank horse or wheel horse?
Forced induction may be your key. I think you could get it NA, but the car wouldn't be very streetable and you'd really have to rev it to see that number and you'd need a ridiculous converter to make it move.
Are you just hypothetically looking at the HP number or do you have a goal to meet at the track? Don't get stuck on a number if you have performance goals instead. There are other ways to make these cars fast and NOT have a 500HP motor, but will act like it does on the track.