Most that run the stuff have done other upgrades as well. Also, they don't use the flex line for the entire length of the car. Mine only has the braided stuff from the sump to the filter, then to the pump, which are both near the tank. Then I am running 1/2" hard line up to the engine bay, then back to braided to go to the carb.
A performance setup will typically run a -6 setup (except extreme cases). This is the eqivilant of a 3/8" fuel line. Most stock setups use a 5/16" fuel line (some 11/32) - which is a -5 AN.
Since you aleady have the line measure the inner diameter of the hose. If it is 5/16" go with -5 AN fittings, if 3/8" use -6 AN fittings. (either is ok in your setup),
Not sure which pump you are using; as c7xr7 points out the stock pump has a 5/16" hard line. Unless you inner dia is 5/16" you will need to change something out. I put on a Summit mechanical and bought 3/8" pipe to -6AN fittings. If your pump already has pipe threads, just buy the corresponding fitting.