Max MPG- slant vs 318/340

Not sure how relevant it is, but in the late 90s I had a 76 D100 2wd longbed with a slant, 727, and 3.55 9 1/4. Driving well in excess of the speed limit on the 35 mile one way commute I had back then, it got like 12 MPG. Swapped to a 318, 8.4 CR, Hedman hedders, stock 360 4bbl cam, intake, and TQ. Running 80 plus for most of the commute, my mileage IMPROVED by nearly 3 MPG. Oh, yeah, then I could actually load something and still keep up with traffic, unlike the slant.

Can't say how the slants work in a light car, but in a fullsize truck with 3.55s and an auto, there is no reason to ever keep the six.