I think I'd stick a painkiller in there, or a C-pig.
That said, if you're after 'Organic' Bro0otalz, you might prefer to go for a normal Nailbomb.
If you're tuning down to C standard or lower, I'd stick with PK. If it's only Drop C, D standard or drop D (or E, does anyone actually use E any more?), then you might find the AlNiCo pickups give you a more organic tone, and in which case, NB or even WP.
Gosh, how very helpful I am!
:D
Roo