To the best of my understanding the valve train (hydraulic rollers and non-adjustable rockers)is the big hold up for high RPMs from a new hemi, the only replacement for RPM is cubic inches, that being said what is the theoretical max displacement from a 5.7 or 6.1 ? If 440 is the most cubes and 7000 is the most RPM it just might not be possible yet...

I do have to agree though they definately have the head flow

I am not causing global warming, I am just trying to hold off a impending Ice Age!