Which intake manifold

There were 370 cfm 4 bbl carburetors, but hard to find today and pricier than a more common 500+ cfm one. In theory, a small 4 bbl carburetor could give better drivability and mileage than a 2 bbl, since at lower power (steady highway driving) you run off just the primary bores which can be smaller than in a 2 bbl. True, the Holley Economaster line might be a good choice. Those were sold aftermarket starting in the late 1970's gas-crisis and generally were smaller cfm than the OE carburetor for the same application. I think they even made a 1 bbl version. You occasionally see them on ebay. If you choose to use the Clifford 4 bbl, I think you need a few other special parts, like a kickdown system which Edelbrock sold (google). While at it, Edelbrock also sold an aluminum valve cover for the slant which is slick, especially if painted a wild color.