I've seen a couple of threads about bad lifters and rocker arms, there's the L99 lifter issue, then somebody posted a pic of their rocker arm that had a manufacturing defect and was hollow (
google cache original thread was deleted for some reason)
so can one reasonably assume that if you buy upgraded lifters, forged pushrods, upgraded rocker arms, proper valve springs, etc you probably won't be vulnerable to the weaknesses of the stock components that were only meant to be used for one application?
I totally agree that these motors should be able to handle mods without power adders. GM has derived the LS9 and LSA from the LS3 engine, so the block should totally be fine. It may just be the valve train components that were designed (for cost effectiveness) not to support high HP/torque applications.