That cam and heads 3/8 line will be sufficient.Figure .5lbs of fuel per hp per hr.Example 300 hp output for one hour would be approx 150lbs of fuel since gas is approx 6 lbs per gallon 150 /6=25gph . Just guestimate your power level use the formula and add a little capacity at the pump for safety for the 300 hp example 35 gph would be over kill.