[petek]

Turk,

(from the installation manual on the MSD site)
TACHOMETERS
The MSD Ignition features a Tach Output Terminal on the side of the unit. This terminal provides a trigger signal for tachometers, a shift light or other add-on rpm activated devices. The Tach Output Terminal produces a 12 volt square wave signal with a 20% duty cycle.

(later in the manual)
No "Tach Adapter" is required for Autometer gauges.

(from the Autometer web site)
It looks like you'd just take the green wire from the tachometer and connect the wire to the tachometer output on the MSD box. I assume the other wire on the tach is black, the black wire would go to ground.