I’ve installed an oem tach and wiring harness with the MSD-6AL ignition box. I’m having trouble identifying where the green and brown wires go from the tach. I think from searching the green wire goes to the MSD box with the diode soldered in line with the band facing the tach but I have no idea on the brown wire. The ground wire is not a problem. Thanks for your help.

I'm not sure where the green wire is coming from. If your using a factory harness, the tach uses pink, brown and black. Pink is hot, brown is your tach signal, and black is ground.

Here's a link to MSD: http://www.msdignition.com/uploadedFiles/MSDIgnitioncom/Products/Ignitions/6420_instructions(1).pdf

Thank you.