Dunno if this will help, but - - My -12 is headerless with the two valve system. There are forward and aft ports in the left tank, and only aft in the right tank. It's placarded left tank for takeoff / landing.
!CAUTION! Most folks who view this website know this, but i am posting for anyone new to PA-12s. Any Super Cruiser experts pease elucidate on this information or correct me if I'm wrong. [Clyde Smith, are you listening?].
Piper installed two different fuel systems over the course of PA-12 production. Early models feed the engine through the left fuel valve. If you open the right fuel valve and close the left one, the engine will quit. The left fuel valve has to be open for fuel to flow to the engine. Later models feed the engine through either fuel valve. With the later system, fuel will flow to the engine with either valve open and the other closed.
As installed at the factory, the physical location of the valves in the cockpit is the only external indication of which system is installed. With both systems, the valves are located on the left forward sidewall. The earlier system had the left fuel valve located very far forward and lower than the same valve in the later system. The early system left valve is much harder to reach from the pilot seat than with the later installation.
You will have to do a little digging with a new-to-you airplane to determine which system you have, especially if the airplane has been rebuilt or any S.T.C.s applied after the airplane left the factory.