Carburetor Question - Is this a good call?

From the above picture, that intake looks like it takes a square bore carb, like most Holley and Carter/Edelbrock carbs.

That adapter if for adapting a Thermoquad or Quadrajet to a square bore manifold.

Even if the secondary bores on the intake are SLIGHTLY bigger than the primary bores, that is still considered a square bore manifold and the adapter isn't needed.