Hehe, that's the thread that made me start to feel stupid, actually
Because there's a lot of good information in there and I still can't figure it out.
OK, I'm pretty sure #5 is for the power antenna. According to the paper from the wire harness:
"If vehicle has a power antenna, connect power antenna wire from new receiver to the female spade connector in vehicle. The spade connector will be on the end of a blue wire which may be covered with black tubing".
That sounds like a pretty exact match (to be honest I only actually noticed that wire is blue after taking the picture).
So I still have no idea what to do with the wire on the right?