Choose postbit_legacy in admincp, erase all code in the Infusion postbit_legacy template (make sure you save a copy of the code in case it doesn't work) and paste in the code from the Infusion postbit template into the postbit_legacy template. OR unselect postbit_legacy in admincp, erase all code in mech fluid postbit template and paste in code from mech fluid postbit_legacy code into postbit template. I haven't tried either, but I can't think of any reason it shouldn't work.
