[Tom Wells]

Xavier,

Here's some cut & paste from MSD:

Aftermarket Tachometers----White Wire Trigger----Magnetic Trigger Connector
Autogage----------------------8910-------------------8920
Autometer---------------------None-------------------None
Classic-------------------------8910-------------------8920

From this table you can see MSD says no adapter is required for the Autometer tach.

Further:

Note #1: There are basically two types of tachometers: Current Triggered Tachometers and Voltage Triggered Tachometers. These (sic) type of tachometer that is on the vehicle may be recognized by the way it is connected to the ignition coil. The drawings below show two wiring diagrams to help in determining which type of tachometer is on the vehicle.

You'll need to use the link in my post above to see the diagrams supplied by MSD.

The major caveat is given as:

Note #4: If the Tachometer is connected to the positive side of the ignition coil, do not attempt to connect this tachometer to the tach ouput terminal on the MSD 6 series unit.

So you may want to ask MSD about your specific application before wiring anything up, although it appears OK as long as you don't use both tach voltage sources.

I tend to agree with mried. The MSD box may have a problem.

Let us know how you proceed!

Tom