You may want to consider a "fuel dot" I believe it's called. It's a third line into the tank and fits nicely into a fitting that can be placed in various locations. It has a nice look. I have used the filler type valves that uses a special fitting on the end of the hose from the fuel supply (pump), but my experience has been they tend to get stuck in the open position after a year or two.
The dot is so simple, there's nothing much to go wrong.

DaveB