wow Gene to get nearly 18MPG outta that beast is right respectable! A 340, w/ a cam AND 4.11's, that Duster just wants to scoot!

Hard to keep the foot outta that one! If you have the 8 3/4" rear it's fairly easy to swap gears, there's another ratio I think 3.94 ,3.76 and 3.55 too...
but need the whole center section, and of course cam/gears, really everything needs to match up right...
wonder if more MPG is available thru changing rods/jets in the Edelbrock? But would need care to avoid going too lean on such a thrill ride! MPG Remedy...?
I've got a '74 Dart Sport, w/ a 225 Slant six, stock except for Super Six intake/Carter BBD carb & Dutra Duals exhaust. The BBD lacks enough "meat" under the throttle blades to Groove it though. I changed the awful 2.76 gears to 3.23's in the 'lil 7.25" rear end. Not many choices for a carb. swap on this one, a 4 bbl is just too much for a stock Slant.
Edelbrock/Carter AFB is my fav. 4 bbl carb, so forgiving and tuneable, AND Groove-able too!
congrats on great results Gene!
Tracy G