Another wiring question

[n2motorsports]

hi everybody, i ran into a road block and don't want to risk shorting anything. in the pic below, the sr blktop harness has a single male end and my s13 (1990) body chassis has a dual female end. i have a single female end that i can solder in but what to do with the remaining black wire?
is that just a ground wire? i looked it up in my fsm and those 3 harnesses are all "engine room harness 2"!?!? any help is greatly appreciated.

Thanks.

http://i26.photobucket.com/albums/c140/n2motorsports/Harness008.jpg