How about the Nailbomb? It cleans up beautifully, not just a metal pickup - for a fairly high output pickup its also very dynamic.
It would be my first choice for that wall of face-melting overdrive that they get on the heavier sections of "MAYH" or "Still Life" (IMO the best Opeth albums).
IIRC Akerfeldt uses a Duncan Full Shred bridge which to my ears has a vaguely similar eq (though not quite the output or as nice sounding as the NB :))
