D4B DC mods like the LD340 DC mods?

There was only one reason those old manifolds had the slot cut out of the divider when they were new and it didn't have anything to do with how the manifold ran or reacted. It was so a Holley 3916 or 4604 three barrel carburetor would fit and work. That was it. I've never liked modifying the center divider, because since most people don't have a dyno in their back pocket, you don't know if you are improving or making it worse. The LD340 and LD4B are two very different intakes. They even have runners on opposite sides. So the mods for one will probably not be optimal for the other. Lastly, as was already mentioned, removing the divider does indeed make it pretty much a single plane intake manifold. So there's that.