In a S2 tank, the fuel pickup pipe make two 90 degree bends, the first where it enters the tank, bends down 90 degrees to the bottom of the tank and then another 90 degrees horizontally where it follows the bottom of the tank where it open ends mid way about 1/8" off the bottom. It would be difficult to stick a stiff enough wire past two 90 degree bends to push out the obstruction.
I would remove the tank, remove the fuel sending unit and look inside the tank to see the condition of the tank bottom. With a long enough pick, you may be able to poke out the obstruction from the end of the pipe. For chemical removal, you might try soaking the bottom of the tank with CLR or coca cola.