[tubman]

I was under the impression that all of the flathead manifold use the old "square" mounting pattern. This was what was used on the early WCFB's and the pre-56 Rochester 4G's. You may have a later carburetor with the larger bolt pattern. I would suggest getting a proper carb, or if you are going to use an adapter, get one for the later Holley (390 and 600 CFM) carbs.