The SH-11 uses an Alnico II magnet so is very different to either a Nailbomb or a Warpig. BKP also do Alnico II pickups but none of them are as hot as the SH-11. Basically you're looking at either the Stormy Monday or PG Blues, however, an Alnico IV magnet will give you many of the same characteristics with a bit more cut so I'd look at those first. The Mule is a hugely popular pickup and is capable of an astonishing range of styles from Blues to Rock despite its low power. If you want a similar pickup with the kind of output you get in an SH-11 then you should like the Abraxas, which is equally versatile and should serve you well. The SH-1 is Alnico V but I wouldn't worry about that too much. Your choice of neck pickup will, to a degree, be driven by the bridge pickup you choose.