software

I'm an old-timer with a 1971 quot;F-seriesquot; Fender P-bass that I have configured to accept a J-style bridge pickup to create a P-J setup. I am so far keeping the original Precision pickups (although I have not yet convinced myself that I will be able to do so). I have a very old SJB-2 Hot Jazz Bass pickup that I bought maybe 15 years ago. Its never sounded right (lots of hum...tone control doesn't work). I am redoing the wiring and have some questions: 1) Do I have to reverse the magnet to pair this with the stock pickups; 2) What size cap do I need for the tone pot? The schematic that came with my SJB-2 indicates a 0.05 mfd. The schematic with my Precision says 0.5 mfd @ 50v. Should I split the difference? 3) I assume that the old SJB is a single-coil pickup. Do I need a ground wire to the bridge if I fully shield the internal cavities? Any advise from you would be welcome. Thanks in advance.