Best way to adapt 3/8 fuel pickup to 5/16 fuel line?

340doc said
Don't over think it. Put a piece of 3/8 hose on and clamp it down. Your talking about a suction line here, not a line under pressure.

I would use 5/16" fuel line and force it on to the 3/8" tube. that way, it's less likely to leak from the smaller tube...