You need hose that meets SAE J30R10, which is rated for in-tank service. Use anything else and the inner liner may last but the outer jacket will fail (become mushy and dissolve).
I know it is available in 5/16" ID for fuel injection in-tank applications, but the racing fuel cells suppliers would have it in larger diameters.
Talk to Jim Harmon at
http://www.harmonracingcells.com/
He's a great guy and will help you. I've bought several items from them.
Rodger