The current American P/J high mass 4 string bridge is a direct replacement for the CIJ versions of this bass. The 3 mounting screws and the thru the body string holes all line up. No modding.
These basses come with no shielding or shielding paint anywhere and are very noisey with the single coil pickup. The pickup itself has a sweet vintage character and a complete shielding job makes the bass usable. Increasing the capacitor from .047 to .10is a good change also.
Aero makes a nice single coil replacement pickup, Nordstrand makes a nice humbucking version. There are others out there too, if replacing the pickup is necessary.
Clubless Club #1