Depending on your budget, there may be a few different ways to go on that. The general idea I'd think of is getting something passive that sounds really natural.
For example, EMG or Delano is NOT going to sound as "natural", but will change the tone to what they want it to sound like. So I'd avoid those.
(They sound good, but are geared towards the more modern, "nu metal" tone.)
Nordstrand makes fantastic, really good sounding pickups that bring out the true voice of the instrument... but are pricey. If you can budget for a set, I'd highly recommend them.
Duncan makes some pickups that aren't as expensive and still sound really good.
Me personally, I can't stand Bart pickups. I feel like anything you put in there will be an improvement over those.