Chip, I disagree with you regards the failure levels being equal for a con-rod in a N/A to forced induction engine. However I really can't be bothered to explain all the differences. Suffice to say rpm has a huge effect on con rod failure, and this is usually in the form of big end bolt failure, irrespective of what type of fixing is used. Shank failure is normally attributed to detonation issues OR extreme forced induction engines.

With regards to the original question for a cossie engine over 8500rpm you will require a different crankshaft and con-rods with revised geometry, suitable cams and solid lifters and suitable valve springs. No point in being any more specific than that as each application is very different.