The SH-1 59 and SH-2 Jazz are classic choices to pair with an SH-4 JB in the bridge. Some people, myself included, really like the Pearly Gates neck.
What are you looking for from the 2nd pickup? Any characteristics or qualities that are important to? What style of music do you play? What amp are you using?
Yes, this depends on what you want out of a neck pickup. The most popular choice is the Jazz, followed by the 59. But this also depends on what you don't like about your current neck pickup, too.