What does this connector go to?

[JD08 42]

I'm trying to figure out exactly how the sport lamp switch connects to the harness. The only available connector I have is the one shown below. any ideas?

 

[Midlife 815]

That connector goes to an optional head-light on relay.  Most Mustangs of the 69/70 era did not have that optional feature.

[JD08 42]

Interesting. Since I don't see any other unaccounted for connectors, where does the sport lamp switch connect? Did they make multiple harnesses? If so, I guess I'll have to add those wires in.

[Midlife 815]

The sports lamp switch connector comes off of the main harness where the heater switch comes off.  You'll see a white flat plug with locking tabs that stick waaaay out.  That connector is almost unique to the 70 Mustang, so it is quite rare.  There are two and three-wire versions (but two pins); one wire is always gray.