Finding a set of original Super T-4 pickups with Trisound (coilsplittable and series/parallel) will be very difficult, they were only used in the Studio basses and are very rare. The old Accucast B bridge is more common as it was used on many Ibanez basses in the late 70s and early 80s. Many were replaced (I don't understand why, because they're great and solid bridges with a lot of mass). Good thing you still have those Suregrip knobs and the original Velvetune tuners in place though! I recently saw a set of Suregrip knobs on eBay for 200 USD!
It was a BIN, and I've never actually seen them sell, but the fact alone that people are asking that kind of money for these tells you something of the status these instruments are slowly getting!I'm not sure if there is a direct replacement pickup for these. I've never seen any Studios, Musicians or early Roadsters (which also had the big Super P-4 soapbars) with replaced pickups. Only one MC824 with Bill Lawrence humbuckers (guitar humbucker sized) in mounting rings, similar to yours. So not much help here I'm afraid. When Googling for 'Ibanez MC924 pickup' I did find this though:
http://www.bartolini.net/special_instru ... fgs_ib.htm
No specs whatsoever, but worth asking!