68 Wiring Question - GT w/Tach option

Background info:
I replaced all my wiring harnesses, but I took the old out 5 years ago. The new wiring harness is for a factory tach and GT car which is what I wanted. The problem is there is a short 3-wire connector from the alternator to the wiring harness near the battery. The wire colors are:

Black/Yellow
White/Black
White

I know that the Black/Yellow is for the alternator to charge the battery. I can’t figure out where to connect the other wires. I have an aftermarket alternator, so that will make a difference. I figure at least one will go to the gauge, but which one. Also, I have the Shelby console with the Stewart-Warner greenline gauge. Does anyone know how to wire that gauge up?

Any taker's on this question???

I've got the 68 wiring scheme book, but it doesn't show the wiring colors I've mentioned.

Thanks,

Sorry to keep asking if anyone know anything about this, but I thought I would run it through one more time...

Thanks,
David