The point was to build with better efficiency not higher rpm, that 371 accomplished building the same peak power at the same rpm as the 408, both 515 @ 5,900 rpm but down on peak torque 495 tq vs 526 tq , 4,800 rpms vs 4,000 rpms.
That would be fine, but is the cr of the 515 hp / 495 tq 371, maybe a tunnel ram might of made the difference.