If you have an Airtex fuel pump catalog they list the pumps by number. It tells you if they are 6V or 12V and if they are open or closed when off. It also tells you their pressure outputs. You want the pump to be in the open position when it's off if you are also using the stock fuel pump. Your just using the electric pump to prime the system after the car has sat for a long time. The stock pump need to be able to draw fuel throught the electric pump when it's not in use. If you are not using the stock pump then you want a electric pump that is closed in the off positon. The catalog, I have is almost twenty-years old now. If I remember right, there are not that many 6V "open" pumps to choose from. Try to get a pump with the correct pressure you need, otherwise you have to install a separate fuel regulator and for the low operating pressure of a Stromberg carb, those external fuel regulators sometimes don't work and shut the fuel supply off. I went through this with a couple new regulators that shut my fuel off going down the road before I finally got smart and got a low-pressure pump with the correct pressure for the Stromberg carbs. That was twenty years ago so who knows if they even exist anymore, the catalog and the low pressure 6V open fuel pumps.