Before you replace the mechanical pump consider an electric pump.
I have a 46 Packard that is prone to vapor lock and have used one to push fuel past the vapor for years now. The electric pump is located near the gas tank and away from the engine compartment so the fuel is cooler. It is also nice to have a redundant system in case one of the systems gets eaten out by ethanol.
Remember all pumps are designed to pump and not suck. Once the line is filled with vapor it is having a hard time doing it's job.
I picked up a 6 volt electric for less than the cost of the original replacement for my 52 3100.