[blykins]

For an engine of that displacement, it's not hard to get 500hp with good cylinder heads, hydraulic roller cam, etc.

When you start approaching 600hp, you need to start using the larger, rowdier cams, little higher compression, etc. Peak horsepower rpms go up, better valvetrain components are necessary, etc.

Of course the larger the displacement, the easier to make more horsepower.

The 428FE that I built for my own Cobra used Edelbrock heads, a Tunnel Wedge intake, a solid roller camshaft, and it was about 11:1 compression. Peak horsepower was about 550 @ 6500. If you were running this car hard, you would need to shift at about 7000. A solid roller cam needs a little more attention than a hydraulic cam and the lifters don't live as long. I would consider that a minus in the longevity department.

Where reliability starts becoming an issue is if you're drag racing with hard launches, spinning the engine really high, etc.