8 guage yellow wire going into firewall question

I have an 86 gt 5.0. Im putting a new wire harness in (also supposedly from an 86gt) and theres an 8guage yellow wire im confused about. On my old harness it starts from the starter solonoid and goes into the firewall but on the new harness it doesnt, it stops and has a female spade connector ending by the alternator...what do I do? Is the one going into the firewall necessary? If not I could just cut it? I need a schematic...