built up 318 oddly low MPG's? hp rating?
I switched from a 750 DP holley to a 600 edel, and went from 8 to 12 mpg instantly, and thats with a 408 stroker, 727 and 4.10 geared 8.25.
I put in a dana 60 with 3.73 gears.
Then went to a Thermoquad AND installed a wideband AF gage, and got 14+ mpg hwy.
However, when I put in a TKO 600 and further tuned the carb, I got (get) 23+mpg hwy on the interstate @ 70 mph, and 18+ mpg hwy backroads (stop and go, small town, 60 mph tops).
Lose the Holley, get a carter (especially a ThermoQuad), get a wideband AF gage, and learn how to tune your carb. And keep the vac advance hooked up.
My duster runs low 12's (best of 12.003), BTW.