[Extended Power]

Looking for a bit of clarification here.
Few guys here have said that all they did when hooking up their FACTORY dash tach to an MSD system, is hooked the factory tach coil negative wire to the grey tach wire coming out of the MSD box.
Has it worked?
Some have said it worked for a month, then piled up.

I'm using an MSD 6-AL2 ignition box, MSD 8253 coil, and a MSD 85551 distributor.
I also just added a Brother's Truck 0-8K rpm tach dash, and the only 2 wires that go to it in the supplied instructions are, power, and coil negative.
The MSD grey wire is a positive, square wave signal...

Please help!
Thanks!