Miserly /6

I am right there with you. I am bringing my 76 Dart Lite out of hibernation, as it gets better MPG then existing daily driver.

I plan on looking at just about every main component and see what I can do to make it more efficient, at minimal cost.

Plugs - quality, but take the time to dress the ground and index them towards the intake valve with indexing washers.
Wires - high quality aftermarket units, routed to avoid any arcing
Ignition - read up on HEI mod. It bypasses stock ignition box, ballast resistor, and goes to a premium ignition system.
Distributor - remove and clean, grease advance weights, run as much initial timing as possible.
Underbelly pan, from front bumper, to K member (at least) to help guide under car air flow under the K member.
ETC...

I have a budget to work with from selling a flip car. I am going to adjust brakes for minimal drag, repack wheel bearings (might as well while I am in there, synthetic grease), I have synthetic in trans and rear end....ETC.

The only thing that is off limits is major body modification. I am an enthusiast first, and environmentalist and economist (save gas, and save my wallet) 2nd.