Most likely, the carburetor body and/or bowl is warped, and/or there is a burr or foreign material on the sealing flange area(s). Doubling or tripling up on gaskets might stop the bleeding.
More detail might wring out a more helpful answer to this one. Exactly where is the fuel leaking? Bottom, sides, particular corner, top…?
All Holley 1920s had—and continue to have—nitrophyl floats. It is a closed-cell foam material, neither brass nor phenolic.
Designing a carburetor with a bowl gasket below liquid fuel level is engineering malpractice.