IMO....regarding the fuel line size....
3/8" from the tank to the pump will make it easier for the pump to draw fuel from the tank due to reduced suction pressure st the pump, but not really needed. The factory used 5/16" tubing from the tank to the pump and 1/4" tubing from the vapor seperator back to the tank. From the vapor seperator to the hard lines to the carbs, 5/16" was used becsuse the fluid is under pressure and will overcome any piping restrictions. BTW....the fitting connections at the "T" fittings and carb inlets are SAE 45° flare connections and assembled WITHOUT any teflon tape or pipe dope on the threads. Any hose connections, supply line to the pump, pump to seperator inlet, seperator outlet to carb supply hard lines are made with gasoline rated nose and "keystone" style crimp connection clamps, if origionality is wanted or needed. Just my opinion of course.
BOB RENTON