AFAIk: Gibson Tar Back in his Explorer. T-Top bobbins, Indox7 magnet (a kind of ceramic), black epoxy under the whole assembly, hence the name.
They were low resistance (7.5k or something like that), low inductance (4.7H, just like a P.A.F. replica) but powerful thx to the mags used. Black epoxy instead of a regular baseplate was probably a way to avoid Eddy currents, in my understanding.
A T-Top speced PU should come close once deprived of its nickel silver BP, fitted with a ceramic mag and possibly stuffed with additional metal core material in order to rise a bit the inductance...
EDIT: Bill Lawrence L90 in his Strat, too. So his tone was largely due to Bill Lawrence (who designed the "Tar Back").
Never heard of a Tar Back Pickup. Don't know what those are. Never heard of Indox magnets. Never heard of T-Top spacing. I've heard of F-Spacing and Arch Top Guitars though.
I would guess he was using Dirty Fingers back in the 80s.
Wasn't the 500T introduced in the early 90s after they quit using the HB-R & HB-L?
Jabs: I always used a 50-watt Marshall. I had one that had been modded with an effects loop and I put an old Echoplex in the loop. I wanted the echo but it never really worked. But it had a preamp in it and for some reason when I plugged it in, the amp was a bit hotter. I bought a few others but it only worked with this one Echoplex. It added the extra little bit of distortion, which was welcome at the time.