The outside diameter of the stock fuel lines are not what the insides are, a 5/16 O.D. may be less than .300 I.D., less around corners
I try and use a 1/2 O.D. thin wall steel tube for my half way serious race cars, a lot larger than needed is way better than a tiny bit to small
If I can't fatten the mixture up enough to slow the MPG down in the 1/4 mile I don't have enough fuel delivery
My new heads up no prep car will have #12 AN from the fuel tank to the crank driven mechanical race pump on the front of the gear drive for the centrifugal superchargers and other accessory needed to be completive