5/16" Fuel Pump Inlet for 340?

The stock pump definitely has its limits feeding a 340. Is your motor bone stock? If you have any mods at all or are running a Holley carb you need more fuel. If you want to stick with a mechanical pump they do make high volume mechanicals that you can put a 3/8 fitting in. Of course intended use plays a big part also. If its never gonna see over 5 grand your probably fine with the stock pump.