I would NOT buy any parts at this stage. This is not a Holley [ or clone ] & you should be able to remove the air horn if you are careful without damaging the gasket.
Check that needle & seal are sealing [ invert airhorn & suck on fuel inlet ]. If that is ok, gently push floats into WARM water to check for pin hole leak; check float level is 7/16" & make sure floats do not rub against body or bind up somewhere. Check acc pump plunger; if hard, needs replacing.
