Gas Mileage query Holley 318

I bought an AFR meter years ago and always weld a bung just behind the header for an O2 sensor. You can really see how horrible carbs are for economy. They are crude mechanisms and you need to keep the AFR relatively rich. Yeah a modern carb that you can get a metering rod, spring and jet kit would be good if you plan on tuning. How old are Thermoquads now? 45-50 years?