Too much pressure??

Are you sure you set the float right? 1/4" or 5/16" is right for the BBD per my 65 FSM.

The float could well be ruined and filling with gas and so not working with the needle & seat nor regulating fuel level properly. IMHO, a complete rebuild WITH new float is mandatory for a carb sitting this long and being this old. The gaskets will all be dried out.