Small block gas mileage DD magnum/LA ?

I’m a big fan of the 5.2 Magnum. I put one in my 72 Valiant because it was cheap (175 canadian bucks), put the Edelbrock intake on, hughes fuel pump eccentric, put a 3-speed manual out of a Volare into it, an 8.25 rear with 2.71s, with a lean Edelbrock carb I averaged 25 MPG on a 13 hour highway trip. I’ve heard the 5.9 is tough on fuel though.