Are their any humbucklers out now that get a good vintage-y Gibson (thunderbird/eb-3) sound? The only thing that seems to come close are darkstars, and those are single coil!
Thunderbirds had bright sounding pickups. EB-3's had a dark sounding sidewinder at the neck. Which do you want?
You can get Sidewinders from a few different makers. I'm not sure what they sound like though. It's a very muddy sounding pickup. I had an EB-2 and it was pretty unusable live, but the Sidewinder in my '74 Ric sounds good in the neck position.
I've seen other vintage style humbuckers for bass, like from TV Jones.