Let me add some more to my comments....
gearing gearing gearing.... running a hot/fast 350 in my 37 and getting around 16-17 if I'm easy on the gas pedal running a 600 edelbrock with a 2.73 gear.(79 Malibu)
running a 305 reman engine with 600 edlebrock carb and getting 17-18 with my PANEL but running a 3..38 gear.
****Both have the 700R4 tranny with overdrive. 1900 RPM's will get you on down the road at the speed limit or better!