The MSD box should have come with a connector and wire for the distributor. Is it an MSD distributor as well?
From the MSD wiring diagram:
There are two circuits that can be used to trigger the MSD Ignition;
a Points circuit (White wire) and a Magnetic Pickup circuit (Violet
and Green wires). The two circuits will never be used together.
Get the full instruction set here:
http://www.g3ignition.com/images/MSD...structions.pdf