Kevin over at EGC is a good guy. He wound me three TB500 repro pups for a TB500 project guitar, years ago. I still have the pickups but can't decide on a body/neck config. I'm bad at that sort of thing.
Anyway, back in 2006 I emailed Frank Kelleher with technical questions about Jerry's TB500 pickups, and this is the answer I received. What a great, generous guy to answer a perfect stranger with this kind of detail. Maybe someone will be able to make use of this info:
"On one of the first, or perhaps on the first TB500 he
ordered, he requested these features:
3 "stock" pickups (6K ohm single coils)
Bournes ultra pots
3 individual mini toggles (on/off each pickup)
I don't remember any discussion of a reverse polarity
middle pickup, but it was 30 years ago! The wiring I
recall was very straightforward, i.e. any pickup on or
off - parallel - in phase.
However .... that git came back for tweaking not too
long thereafter & I was heartbroken to see that they'd
yanked it all out & put in God only knows what. Active
electronics shoehorned in by someone with 10 thumbs.
Not a clean job to be sure. My fuzzy memory says they
were low impedance pickups paired with some sort of
Alembic type of onboard preamp, but I guess it COULD
have been the P-90 deal. To my knowledge WE never put
P-90s in anything for him, nor is it likely we would
have if asked."