Down in So Fla, Holley's are altitude sensitive and overpasses are altitude! Send the Autolite to Pony carbs w/ the engine specs and you won't find a better one. Jon will build it for your car. My old one got 20-22 MPG w/ a cam, headers, and my belief that if there are 4 holes, they should all be used! It has 170,000+ miles on it and Jon refurbished it @ 160K.