Neutral safety switch and B&M shifter

My car is a 74. I have no idea if it worked before because on my year of car you can't put it into gear until the key is in the on posistion using the column shifter. I traced the 3 wires from the tranny up to the removable blocks that plug into the firewall. From there i have no idea where they go. I am assuming since the reverse lights work ok that the wiring is correct. I know some GM's have mechanical interlocks that you have to by pass in order to get the job done. Could that be part of the problem?