Please don't hate me, but: this story has a simple solution.
Here are your options;
For more performance; moreTM (Torque Multiplication),bigger engine,more air thru-put, more compression.
>For more fuel economy; Smaller engine, lower rpm, more compression
>notice more compression is on both lists.
If you want to spend money, get the compression up.That's a triple whammy; More torque, more power, and more mpgs.
this story has a simple solution;
a bone stock LA360 with a 318 cam and no more than 3.23s. I'd even put the 318heads on her.
It costs pretty much the same to repiston a 360 as it does a 318,and it's way easier to make compression with the larger swept volume of the 360.
A big engine operating at a lower rpm might make at least as much economy as a smaller engine operating at a higher rpm. The problem often is that the smaller engine suffers in the performance arena.
A 360 has no problem pulling even 2.76s with the tallest tires you can fit. But 2.94s will get you about 50mph@5000 rpm,in first gear, so I like those.And yes the 318 cam will go to 5000, even 5500. but it's kindof done at 4500 to 4800 with the stock 318 heads.
Then a matching port-size intake,a metering-rod carb,a free-flowing exhaust, plus I'm a huge fan of fresh cold air into the carb.