The stock fuel lines are good to about 125 mph. To put this into perspective, the stock fuel lines are crimped down to a .257" at each fitting. That's roughly a 1/4" fuel line. Most guys go with a -8AN to the fuel rail which is more than enough to feed 1000+ hp at 60psi fuel pressure. The pump feed size is more critical than the pump to rail size, in that it is a suction line, and most EFI pumps are not good sucker pumps. Mounting the pump behind the tank or better yet in the tank is the best way to plumb it. The pump should be at the lowest point in the system, in that it is lower than the tank, and behind it, so gravity and G-forces are in your favor.
A -6AN line from pump to rail will supply enough fuel for over 800 hp. at 65 psi. Most Sprint cars run a -6AN feed line to their injector valve, and they run methanol which requires twice as much volume and it has a higher specific gravity. They make over 650 HP with one -6AN feed line and they run around 60psi fuel pressure.
The problem with running a huge supply line is that the pump has to push that entire column of fuel under 1+ G at launch. The pump has to work harder to push the weight of the fuel column to the fuel rail.
So, to answer your question, you need to have enough cross section to feed the power out-put of your engine. A -8 is typical but usually WAY over kill. Again, consider that the stock line size is necked down to a 1/4" in 4 places, and it will feed over 600 hp.
Good reading here.
pg 76