s13 w/ rb25 wiring issue... power fc

[tpetrucci33]

Ok so i have a 89 s13 w/ a rb25. I have 3 wires coming from the power fc that im not too sure where they go. Here they are...

Black/Red pin#107 - power ground
Black/White pin#49 - power supply
Gray/Red pin#43 - start switch

Any help or input would be great.
Thanks