I'm not entirely sure if I understand... are you talking about can you use a remote fill valve or do you have to use the one on the cell?

Either way - realize that it's financially and safety-wise in your best interests to use the fill cap on the cell. If you fit a remote one, there's need to fit all kinds of safety bits like check valves etc in case the hose is ripped off in an incident. Even so, it's still safer anyway to just not have bits that can rip off and spill copious amounts of gas. Instead, you can have a filler that's blocked off from the driver's compartment entirely.

I'm going through this now on my DSR thanks to a legacy long filler neck from the FF I'm converting; makes me glad all over again that I didn't put one on my IT car...