It's kinda within an interim period, during which they were putting vacuum actuator to close the fuel supply when the engine wasn't running.
Quite simple in that there's the normal selecting tap, but also a means of stopping the fuel with a vacuum operated diaphragm. That just opens supply only with motor running and you don't have to remember to switch tap off during non running.
It will work with both fuel pipes T'd together and connected to the tap you've ordered. Then the vacuum pipe (looks like the brass one in your images) would need to be closed.
Of course, you'll need to just switch fuel on and off manually in that configuration.
