A 500 cfm is plenty for a stock 318. A 750 is way to big for a 318, the 340 intake manifold would cause port mismatch. The op said that his 318 is stock. Go with a weiand action plus intake manifold and a carb spacer and a edelbrock 500 carb. Also go with a good flowing exhaust system, a 2 1/4" system is fine