The tab is attached to the arm for the throttle and choke shafts, retained with a washer and cotter pin. It's the return spring attaching point. The other end of the springs are attached to the heat shield. Three springs in all, IIRC, all the same.
Photo is the choke actuating arm and cable receiver.
As Mickey says, the filler point for the transmission is the dipstick hole. a real PITA to remove the dipstick, also to get oil into the trans. Funnel with a short piece of hose works best.