J-P-J configured bass

Fender had a Stu Hamm model in the 1990's that was a J/P/J. As I remember, that bass had a switch to go between the neck J and the P, and was active. A friend of mine who took a trashed Rick and rebuilt it with three pickups wired it V/V/V/T with the four knobs available to be placed in the routing of a Rick body. Anything you like will work. If the pair of J pickups are RWRP, you could put a series/parallel switch on them to get a full sound and be humbucking like the P pickup. Fender Bass VI wiring was three off-on switches, one for each pickup, and the "baritone" switch, an in-line .0068 capacitor to roll off the low end, kind of like the .0047 stock on a Rick 4001. Somewhere else on the forum is a thread with links to many wiring diagrams.

Just for stability so your bass will last: do you have a friend with a router and a clean bottoming bit to clean up and even out the pickup routs? If not, sometimes the shop teacher at a local school or a hobby woodworker/furniture maker friend/acquaintance might help you out.

This will also give you the ability to put some foam rubber under the pickups so you can adjust their height with the screws to even out the string response.