Coupla things: Unless it was modified, the pickups are probably not J99s.
When the mods are done, if it's a Carvin body and neck, then it's a modded Carvin, IMHO. If the neck isn't from Carvin, I'd say you'll have either a parts bass or a Franken-bass.
The J99 pickups showed up in 1999, so that's almost certainly what they are if they're not stacked humbuckers.
Also, Carvin started putting the Hipshot B bridge on their basses back in 1998. Unless someone swapped the original out, you've already got a Hipshot on there.
tasty !