I just got done a P-Bass Frankenbass that I built. I got all the parts from Bass Parts Resource, and I pickded up the Fender '62 PBass Pickup, two CTS 250K Audio Taper Pots (my preference I use them for both volume and tone), a Mallory .047uf Capacitor and Switchcraft Jack. I have also had good luck with the electronics from Mojotone, and I love their wire. They have nice vintage cloth wire, as well as a really nice braid shielded wire that I have used.
Don't forget a couple things, first if your going to redo Pots, Caps and pickups, do the Jack too. That way the whole system is an upgrade, second when you get up to the better pots and jack, you might need to enlarge the mounting hole. Make sure you are aware and prepared for that. Good luck!!
Fender Jazz Bass Club # 985, Official Bassman Club #84
Fender Active Jazz Bass, BCG P-Bass, Fender Bassman 135 + 215 Cab, BFM Jack 210