5/16" Fuel Pump Inlet for 340?

I mentioned this on another post. There is a preformed hose that goes from 3/8" to 5/16". I'm not sure it is long enough to go from your 3/8" main line to the pump inlet. It might be a couple of inches of short, but you could just extend your 3/8" line with a small connector piece. Cost is about $10 on eBay.

Definitely do NOT replace the 3/8" main line that you already installed. That should work fine.