need help wiring a factory tach

[flatheadfever]

I installed a factory tach in my 83 wagon. I plugged it in and never looked at any of the wires under the dash.
I went over to buddys place and we took the wire from the dist to the plug on the harness fire wall from a junked 442.
I plugged it into the sameplace on the harness on my wagon and nothing happened.
Facing the firewall it was the left plug, top right corner that the wire plugged into.

Could it be that I have the wire plugged into the wrong socket on a PONTIAC?

Does anyone know which plug is the correct one for a TACH on the fire wall plug?

 

[pontiacgp]

it's a brown wire that goes thru the firewall and joins up with a white wire. It does not go to the harness on the firewall...

 

[flatheadfever]

it's a brown wire that goes thru the firewall and joins up with a white wire. It does not go to the harness on the firewall...
The 442 that i took the wire off had a pin in the harness plug.
I wonder where the factory penetration would be if not the wire harness plug?