5/16" Fuel Pump Inlet for 340?

I run my 360 Magnum with an autozone airtex $20 pump, demon 650dp, 6.5 psi regulator, 5/16" sender/3/8" fuel line/5/16" pump inlet, 3/8" pump to regulator to carb. Your pump should be fine and a properly tuned 650 is plenty for real world and also when you do the math. My 60' time is .15 quicker with a 650 vs 750. Throttle response is also better with the 650.