Mystery Ignition Box

Rather than worrying about having a spare, why not return it back to stock points?

Or buy a points dist and keep that as a spair in the trunk. Pull cap note location of rotor, unbolt dist hold down, disconnect wire from neg coil, jumper from ballast to coil if it does not already go there. Install point dist noting rotor direction, Attach point dist wire to neg coil. Fire it up. You might need to time it by ear if you did not bring a light with you.