1988 Alternator wiring

[docrock]

I installed a TBI 5.7 out of an 88 van in my 42 Chevy truck. The install is going well and running. There are 3 wires, one is a larger red and goes to battery. The brown wire comes from the connector at the alternator goes to a dash light and then a wire goes to the on position on the ignition switch. The wire in question is a pink with a black line, where does it go?
Thanks for any help