72 P-Bass wiring question

[ScottGrahamMpls]

Hello experts. On my 72 P-Bass I have a single white wire leading from the pickups to the controls. I also have a black wire that starts at the output jack, is soldered to the back of both controls and leads to the brass plate that is beneath the pickups. There is another black wire that leads from the brass plate beneath the pickups but leads nowhere. It is about 2" long. Where should it terminate?

Also, where can I get new foam for "springs" beneath the pickups. Mine is hard as a rock and will not exert any pressure against the back of the pickups.

Thanks!