Actually the Stingray pickups are not active but the basses are equipped with a preamp wich make the bass active. This means that you could stick with your OLP pickup and add a preamp from Basslines, Bartolini or Aguilar for example. Basslines and Bartolini also have Musicman style humbuckers if you're not happy with the stock OLP one. Either of these combinations will improve your sound significantly although neither of them will make your OLP sound exactly like a Musicman. As far as I know, the Basslines pickup and preamp are closer in sound to the original but Bartolini's are also well known for their high qualilty althouh the might sound a bit more hi-fi. I'm not a wiring expert so I don't know how much work that would be involved.
As far as I know Ernie Ball doesn't sell pickups or preamps separatly, only as spare parts which in practice means that you need to have a broken Stingray pickup or preamp to send to Ernie Ball to get a new in return. Greg, please correct me if I'm wrong.
Basscat
