Horsepower limit for out of the box Edelbrock RPM heads

Ive got a 408 with eddy heads . The porting is stock but they have larger inlet valves 2.08 from memory . It dynoed 515hp and 535 ftlb.its running a 750 holley and dual plane inlet with a howard hydraulic roller. Ive ran 11.2 at 120 in a street car through a 727 and 3.9 gears.i would dearly love to run an 11 flat . Will a port job get me there ? Im in australia so theres no cnc program that i can find for my heads . I know a fair few stock eddy heads on 408's that are around 450hp and that seems to be the norm.