http://www.carvinguitars.com/pickups/
This will get you a start. If you search the pickup and electronics forum for Carvin, you'll get a good amount of info, too.
Basically, the soapbars are deeper and more hifi sounding, the J99s are closer to a Jazz Bass tone. The H50s are somewhere in between, I'd say, but closer to the J99s. All of these pickups are available on both the Icon and LB70.