I can't comment on a specific brand or model. But one option that has been kicked around is wiring the pickups in series rather than the standard parallel. It is said that doing so will get a fatter tone, closer to a Precision but not quite there. A suggestion has been a series/parallel switch. Series vs. Parallel Another thing, I would solo the neck pickup and turn down the tone knob (I was just goofing around with the idea last night). However, doing so would rob the jazz pickup of its distinct tone. If you did that, would it be worth replacing your current jazz pickup?
I guess some kind of split coil pickup would sound the closest to the precicion pup. DiMarzio, Bartolini, Aero and Sadowsky makes them. Probably others to. Check out this link: http://archive.bassplayer.com/z1999/9903/pickups.shtml
The J neck is in a different location than the Precion pickup. As per my conversation with Bill Lawrence, the J has tall, skinny windings and higher flux leakage. The P has short, squat windings and lower flux leakage. Apples and Oranges. I sold my Fender RB5, because I want a P tone, and could never coax one from the RB5, no matter what I did for strings or settings. To its credit, the RB5 nails the vintage J tone.
I've been on a search that was similar to yours. I wanted that P Bass tone, but I didn't want to go out and buy a P Bass at the time. I did have an '80s Jazz Bass that I didn't mind doing some modifications on. After doing some research on the net and in this forum, I selected the Duncan "Hot" Jazz pick ups. I've played the bass with both round wounds and flats, and I can get pretty close to a P Bass tone. Ofcourse, it not quite exactly a P Bass, but it's close. I ended up buying a P Bass anyway about 6 months later. If you really want that P Bass tone, and I think most of us here at TB usually do not "settle for less", you may as well start saving for the P Bass, cause you'll eventually buy one anyway.
