Fuel Line Choice and size

Brooks James said
I was thinking cheap, if he has an engine that needs more than 120 gph, ( 2 gallons a minute) or (2) (55+ gallons drums worth an hour), then by all means, go 1/2 inch

Well, if that's his stuff in the pic, he's got about $700 worth of pump,regulator, fittings, and relays.
And a 300 gph pump.