One option for the factory fuel tanks is an "auxiliary fuel port". This port is designed for fueling generators, heaters, etc. It's available as an option for gas or diesel.
If it was ordered on the factory invoice, it may not be on a TransferFlow (SMB) or the Quigley replacement tanks. You'll have to check and see whats there. You might have the extra fuel port on your sending unit.
Tapping permanently to the fuel tank is an option.