  We introduce and study an extended "t-U-J" two-orbital model for the
pnictides that includes Heisenberg terms deduced from the strong coupling
expansion. Including these J terms explicitly allows us to enhance the strength
of the (pi, 0)-(0, pi) spin order which favors the presence of tightly bound
pairing states even in the small clusters that are here exactly diagonalized.
The A1g and B2g pairing symmetries are found to compete in the realistic
spin-ordered and metallic regime. The dynamical pairing susceptibility
additionally unveils low-lying B1g states, suggesting that small changes in
parameters may render any of the three channels stable.
