Check further in this forum for the Aftermarket tach question thread... I just installed a Sunpro tach in my '05 STX with the 4.6 V-8, and you'll find all the info in the thread... I had to purchase an Autometer tach adapter #9117 ($75.00 from Summit). This sets up the correct signal for COP and DIS ignition systems. Once installed, it was a no brainer, and the tach works great.