I have agreed that its possible with a turbo though it would be risky to generate that kind of power for long without some upgraded internals.

What I stronly disagree with FordMan on is that he thinks that kind of power is possible with a normally aspirated stock shortblock.

As I have said its possible to get that kind of power from a NA 5.0, but there will be nothing stock about pulling it off.

I have also been lucky enough to ride in a 600+ HP 935 race car which to most people would just appear to be a stepped up version of my car, but it takes quite a bit of aftermarket components for a 3.4 L engine to repeatedly put out that kind of power for almost 24 hours.