No Replacement for Displacement (myth or fact)

What has NOT been discussed is that the most important factor is intake valve size and that is determined by the cylinder bore size. (Note: for a turbo the exhaust side is more important than the intake but that's a whole 'nother discussion.)
So if a larger displacement allows larger intake valves it will have more torque and power throughout the rpm range. With a 273 the valve size is limited by the small bore.