The worn pump well lets fuel seep by the rubber plunger after the carb warms up, as I understand it. I tried everything I could think of to make that carb work, float settings lower, fuel pressure down to 3 1/2 psi, new accelerator pump parts. Nothing worked. A Holley does now though.
It is hard to prove that that is the problem for absolute certain, but I had some thoughts on possible repairs. Maybe just a hone with a real fine stone and polish it?