On a different brand 300 CID 6 cylinder (that brand with the same name as a 50's country music star from Tennessee), I used a 400 CFM Carter AFB on an Offy intake. Worked very well, but was really too much carburetor for a truck on the street.
The van came with a single barrel Holley. The conversion made quite a bit more power and more than doubled the fuel economy! Like having one's cake and eating it as well.
Jon.
