Aerodynamic upgrades?

My commute might be changing in the near future, so I've been thinking about trying to optimize my 67 Dart to get a little better gas mileage as it might be turning into my main daily commuter. My current setup is a modern 5.7 Hemi with a T56 and 3.55 rear gears, so I've got a fairly low cruise rpm and have got it up to around 20-25 depending on the conditions (~20 is my average, 25 only on real flat road). I think I might be able to squeeze some more out with some tune optimization, but ultimately I know I'm pushing a brick through the air, so I'm curious if anyone has done anything specifically to try to address that. Off the top of my head I'm thinking maybe something like closing off the engine bay better and maybe something like a front splitter or other sort of front aero to clean up the airflow, but I'm curious if anyone has any examples of those kind of mods as I'm guessing they aren't exactly off the shelf parts. Would be curious to see any pictures or designs people have put together over the years. Seems like a lot of the stuff out there is for the later model 70+ cars, but may always be able to adapt those ideals to earlier cars.