Fuel Filler question 1966 C10

[66C10LB]

I have built my idea of a fuel filler setup for my 66 C10. I am not very experienced with fuel systems so I was wondering if others know if it is important to add a fuel overfill/vent connected into the filler neck close to the filler cap, OR if it is enough to run a fuel vent line that is not connected to the filler neck using hose and a rollover valve. (Fuel filler is positioned on the INNER wall of the Fleetside bedside) Any ideas would be appreciated. Pictures for reference....