Bryan,
Have you verified [with oscilloscope, CMOS logic probe, or Noid] that there is a pulse train at the Black/Violet wire going into the tach??? The 'TD' signal from the SC Bosch CDI unit should drive the 3.2 tach just fine, but something may have caused a problem with the TD signal from the CDI, such as D8 being blown. There must be continuity from CDI unit to the input lead into the tach when checking for a signal, that is, the connection must be normal, not disconnected when checking for the pulses!
There is documentation on the SC CDI unit in this thread:
6-pin SC/Turbo CDI unit repair documentation