When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
GM claims that the stock L98 engine is "designed" for a maximum intended horsepower of 350@5700rpm.
But I'm sure that others here would tell you that the stock L98 is capable of considerably more. You have to figure that GM's published numbers incorporate a safety factor.
You can find these numbers from a couple of "official" sources.
One is Chevrolet Power by HP Books. A great source of Chevrolet-only engine information from the small block V8s to the 60 degree V6 screamers.
Another good source (and probably more up-to-date) is the GM Performance Parts cataloge. Lots of good tid-bits of information, but contains info on Pontiac, Buick, and Oldsmobile engines as well as Chevrolet.