Interesting discussion about using G&L Humbuckers in TBird builds. I will be very interested in the outcomes.
I have a G&L Asat, which has the same fancy electronics and pickups as the L2K, except in a Telecaster Guitar body. Mine has the 1.5 inch nut width and a lovely flamey neck. Here's a pic. I have a Hipshot drop tuner on it and it works really well on this neck and I dressed her up with a pearloid pickguard from a Cabronita.
It is without doubt one of the hardest hitting basses I have ever played even in passive mode. Certainly a bass that was on the gig roster until a TBird and a LP Double Cut muscled in. The pickups are monstrous and extremely versatile, really Swiss Army knife stuff. The active modes are not for the faint hearted- plenty of guys I know with G&Ls don't run them active. The Asat is also the reason I haven't kept any Stingrays, it does that type of sound (and many others for that matter) but "nicer" in my opinion.
As for pickup position- the pickups in my Asat are pretty much in the vintage positions for TB IVs. If you are only doing single pickup I would definitely put it in the TBII position. It will be plenty.
One thing to be aware of with these pickups is that the magnets are incredibly strong. It took me a long time to track down that they were the cause of some inexplicable fret buzz I was getting on a perfectly set up neck (the G&L necks are beautiful BTW- get the 1.5 inch one, if you like TBird necks). I was discussing the issue with the Australian importer because it had me stumped as to why I was getting the buzz and he suggested that I ensure that the pickups were screwed down into the body as far as they will go otherwise they can pull the strings downwards slightly and cause unexpected fret buzz. Screwed then right down- no appreciable drop in output and the buzz went away.
And wasn't Nick Seymour's Midtown just fantastic in the Crowded House concert? Just goes to show what a load of rot gets generalised about Gibson basses.