340 or 408?

I think another thing that is missing from this conversation is mechanical efficiencies of the system as we go up in RPM. These are just generalities but the harder you push a mechanical system the less efficient it tends to become. You make more heat, greater friction losses, etc.

Maybe this is one of the "little things" but I'd imagine that there's a Goldilocks zone of displacement and rpm where the rest of the combo exhibits the best overall efficiency.