Fuel line? Is it enough

IMO a return line is important as well. My 340 (330HP rear wheels) runs fine on the 5/16" feed line, but craps out at top end in warm weather at Brandimere (5800'). Once the sun sets, it runs great to 6500 RPM. I am running a factory return line that was part of the vapor recovery system on some 70's A-Bodies. The line runs parallel to the existing feed line. I am setting up a filter with a vapor separator and purchased the 3/8" pickup for the tank end. A reducer from Goodyear adapts the 3/8" tank pickup to the 5/16" line, so if I ever want to go to 3/8" fuel line I already have the pickup. A cool can and carb insulation gaskets also help with todays alcohol laden gas. Remember that alcohol increases RVP and causes vapor lock a lot easier than non alcohol gas.
Good Luck,
Bob