Like IQ52 said, if you throw enough money (and cam) at them you could reach that number.
I would guess the F.A.S.T guys and NHRA stock class guys have heads that would get to that number. A 4.25 stroke thrown into a meaty 340 block would go a long ways.
Also, you could have someone with a real "happy" dyno get whatever numbers you want. Horsepower on paper at the flick of the wrist. :evil3: