Before trying to adapt the Narrowcast circuit to the Simulcast PCB I would just try socketing Q2 and try using a low HFE silicon PNP transistor - such as 2N2904, 2N2905A, 2N3703, etc, and using trimpots for R7 & R8 in case OC71 leakage (unsure if this is the case, but rather safe than sorry) has...