tach wiring harness. where to connect?

[Gregsmx]

I am upgrading my instrument cluster with a tach. The tach wiring harness has 3 cables:

Brown, which is a long cable and has a rubber firewall grommet on it indicating it goes into the engine compartment somewhere.

Reddish pink, which looks like it stays under dash.

Black. This is a ground wire.

Can someone tell me where to connect these 2 cables?

To make things more interesting, I am also installing a Painless wiring kit. Included with the under dash wire cluster is a pink wire labeled "Tachometer". So the question is which wire does it connect to, and where does the other go?

Thank you, Greg.