dual quad small blocks?

The D-64 & 66 are small port manifolds. To seal well, the top of the ports at the head should be built up and the port mouth reshaped.
I'd certainly buy a new big port dual quad Edelbrock if they made one.
Exactly. Place an LA 340/360 intake gasket on one of those Offenhauser dual quad manifolds and you'll see why they cannot be bolted to the 340/360 head and actually seal. The SB 340/360 671 Blower kits used a modified dual quad Offy with welded up port areas. The welding added material and thus allowed them to enlarge the port to 340 size. A dual carbureter non tunnel ram intake manifold was never made for the 340/360 head. You can currently get an Indy Mod Man. But as a dual quad manifold its not a good street intake- but it looks great.