Big horsepower 318 builds

The 318 in this article only spins 6500 rpm to make 477 hp, don't thing you would need another 1500 rpm's to make the last 23 hp.

Iron-Headed Mopar 318 Magnum Engine- Popular Hot Rodding Magazine

But it's a very well put together engine.
And that motor made a lot of torque as well. To me, there has to be a ton more thought in a smaller motor, not necessarily a ton more rpm's. For instance, a 440 has a lot more "wiggle room", if you will, for error in the build and still make decent power. Throw a few errors in a 273 build and you might get beat by a good super six in a volare... lol.