If you havent already done this - consider doing the following: electronic ignition (consistantly more spark energy), run as much advance as you can without detonation, run a clutch fan, (a little less drag on the motor), install a highway 276 gear or taller rear tires, (that'll slow the motor down at speed). Install a spreadbore 4 bbl, like a TQ or quadrajunk, these really have small primaries vs a holley or afb. The other thing I have found is the 340 stock cam really does nicely in terms of getting pretty good mileage with a balance of performance in the daily driven small block. You just need to determine where the balance is, you dont want to ruin parts by running too lean or too much advance.
