Anyone have experience with a 4bbl 450 CFM Holley Economaster Carb...

A friend of mine had a late 70's Chevy Crewcab 3/4 ton pickup with a 454. He got 9 or 10 miles per gallon. He thought he would be thrifty. He built a 283 with a mileage cam and one of those 450 spreadbores. Guess what-10 mpg and a gutless pig!