Need recommendation for a Carb for better MPG!

Cheapest to improve mileage?
A good tune, vacuum gauge and taller,narrow tires. Also a decent wheel alignment.
But as mentioned, a guy might be better off just putting the money in the tank. 17 mpg is totally acceptable in a vintage hot rod.

Like spending $45,000 to get a new economy car, how does that make sense? Could drive the wheels off the old car and be money ahead 10 years later..