Would anyone happen to know if you can purchase these on their own?

I was going to experiment in putting them into my ESP SV.

Which will either be great, or horrible.

And I don't know much about their pickups, so I'm open to specific suggestions. I'm going for an Opeth-y tone.
Pretty much go with either the Tremonti or HFS. As for the neck I'd recommend either a Vintage or Dragon Bass.
This is a totally lame question...

but as far as the Bass and Treble pickups go, where do (typically, since its obviously up to the player) each go (as per Bridge/Neck)?

Treble in bridge and Bass in neck?