4 barrel 318

There is no such thing as a "318 4 barrel intake". The factory never made one with the smaller ports for the 318. They all used the 360 intake manifold and mismatched the ports right from the factory. The only exceptions to this were the 273 4 barrel intakes, which did have the smaller intake ports. I would use the 340 intake. That's a fine piece and will run well.