Greg, if the pickup coil wires to the ignition module is reversed the following will happen (that I can think of):
- Timing will be way off - but likely can be “corrected” by rotating the distributor body. This is because the ignition module will now trigger spark from the wrong edge of the “sine wave” that comes from the pickup;
- the rotor will not be well aligned with the HT terminals in the dissy and could even jump to the wrong spark plug;
- spark timing will not be very stable because the 0-crossing point will be less well defined;
So, yes, it is VERY important to have the pickup correctly connected to the ignition module.