I'm sorry, but the stroke is not the cause here. My personal 408 makes power through 7400. Dyno tested and confirmed, and My heads only flow 285. This is cam, cam degree, carb cfm, or intake manifold choke.
Heck, the BluePrint 408, with a much smaller hyd roller cam makes hp through 6400 or so. With as cast, edelbrock heads and an airgap.