If your Holley is rich you don't know how to tune one. It's that simple. IMO, if you want a hot rod and are worried about fuel economy you need to take up a different hobby or spend the $$ on a good fuel injection system.
My street/strip 69 Dart has a 434" small block, a decent sized solid roller, 263/271 @ .050", .711/.719" at the retainers, ported Indy heads and intake, 11.2-1 compression and runs on pump 93. The carb Has a BLP BX4 1.590" venturi main body, 1050-1100cfm according to BLP. This car gets driven on the street a lot and runs mid 6.20's @ 110 mph in the 1/8. It hasn't had the plugs changed in over three years. I don't know how many miles per gallon or gallons per mile because it doesn't matter, if it did I'd have a Prius.