We know the 360 has to turn 7500 to produce the peak hp. In 7500 revolutions the 360 ci engine moves 2,700,000 cubic inches of air. The 408 will move the same amount of air in 6618 revolutions. May not be exact but I bet it is close. A friend did this with a truck. He built a new 408 short block and used all the parts off his 360. Truck was about a tenth faster and that was it. He had to lower his shift points.