It all depends on how you reach that goal. Boosted by anything on the crank, it won't last long. Nitrous, it won't last long. Turbo, it will last a while as long as the tune is on. Naturally aspirated the ceiling for most commonly available race-type small block heads is 650-700. The issue with the blocks is main structure, and cylinder wall integrity. If you plan to exceed the 600hp, it's just stupid not to upgrade the block. Some guys have done it and they last. I suppose that should mean everyone should last. But that's not reality.
