For simplicity, I would look at a Q-JET or the Edelbrock, both will be easier to tune then a Holley. Holley was intended for racing, still is in my opinion, the Q-jet is a proven carburetor that does well on all sizes of engines, and the Edelbrock is a copy of one of the better Carter made carburetors. Any adaptor will hinder the performance, and as for fuel mileage, that ship has sailed. I would expect 7-9 mpg, the Q-jet will likely give the best mileage due to the small primaries. Ideally, fuel injection would be the best choice, a self tuning one.
Joe
