If you are looking for mileage AND performance when mileage isn't the main goal plus cheap, you better become a Thermoquad guy.
Properly set-up they can't be beat. I have a buddy with a 78 Cordoba with a 360 Mag in it. 4000 lbs 3.21 gear on 275/60/15 rubber. Mild cam maybe a step or two up from a "good" stock 340 cam, headers, M1 dual plane and a finessed TQ. Has run 12.90's on slicks and gets 22 mpg highway.
