Any modern engines or engine builds for modern results?

Something else to consider from the efficiency aspect... building an engine with good quench (closed-chamber heads, zero-decked block, flat-top pistons) will allow you to not only run a higher compression ratio but it will make the best power on a leaner air/fuel ratio and it will continue to run smooth at leaner cruising mixtures; as in a quench engine can smoothly run on 17-18:1 A:F but if you try doing that on an original 340 with open-chamber heads it will probably surge and eventually overheat and/or ping. Point being that all saves gas because you're using less fuel to keep the engine turning.