Ok, lets face it the only thing that improves the fuel rating is the air flow, compression, spark, flowers, headers, fuel flow. shocks, psi for the tires, weight, and airodynamics. The number of ports only helps with the injection and and extraction. It realy does not help fuel rating only performance.
Also let it be know that if we learned anything from the cars from the 70's it is that you can not make a big block v-8 have a better fuel rating by lowering comprestion and de-tuning them. Its like giving a jet a muffeler to decrease nose.