Here's another question though... I see that the MSD requires another "box" so that you can feed the stock tachometer. I've looked at the wiring for the MSD 6 series and that doesn't make sense to me. Where exactly, is the stock tach getting spark signal from? What I mean is... I'd always thought that it got it's feed from the wire going to the coil. The MSD appears to get it's signal from that same wire so why would you need to feed the stock tach differently after installing the MSD?
I think this is because the Factory Tach the MSD Have different ways of inturpiting the signal. So the Tach Adapter is taking the info the Tach Output is sending the Tach and converting into the style of information it needs to work correctly.
On a side note I wonder if this makes the factory Tach's more accurate?