I went with the bundy tubes as well :) 5/16 I think.
From my understanding the fuel soaks into the seams of the fuel tank and that is what will cause the explosion, even if properly drained and ventilated.
I intend to take my tank to a Radiator place (had some work done through them in the past) to have the top soldered onto my UTE tank. (In-tank Bosch 040 pump)

Sorry to hijack the tread but I was wondering what people have used to hold the fuel lines in place under the car (run along the chassis Rail). I intend to run 2x 5/16 fuel lines and the rear brake line next to each other and was looking for a clamp/multiple clamps to hold them in place??