[bobcowan]

With good quality (not exotic unobtanium) forged rotating assembly, a stock block is probably good to about 6,500-7,000, depending on load.

The limiting facter is usually the valve train. If you use the right parts, a hydraulic roller can safely run to about 6,500. Standard parts (like stock lifters and springs) lowers the red line considerably. As said above, the chevy 427 can run to 7,000 by using a lot of expensive and exotic valve train parts.