Here’s some interesting comparative finds on Thunderbird pickup spacing through the ages as traced out from my basses…
View attachment 7490740
Neck pickups:
Basically with the template held at the 20th fret you can see that the Gibby 1967 NR II pickup is in the exact same location as the 2012 Epiphone CP and the Epiphone VP as well as the newer Epiphone 64 Reissue neck pickup.
The 1979 Gibson Bicentennial bird moved the neck pickup closer to the neck by about a third of a pickup width.
The Gibson 2013 Anniversary, the 2021 Gibson NR Reissue and the 2015 bird were all bumped even closer to the neck, as was the 1991 three pickup Thunderbird.
Conclusions - if you want to hear what a vintage bird would sound like with TB+ pickups, get a 2012 CP (to my ears the CP sounds warmer). It looks like Gibson repositioned the neck pickup closer to the neck when they reintroduced the Thunderbird for the Bicentennial launch and kept moving it further from the original position even more towards the neck as time went on.
Bridge pickups:
The 2012 CP, the 2019 VP and the new Eppi 64 reissue all share the exact same bridge pickup location. Unfortunately I don’t have a vintage IV reverse or NR to get a bridge pup location from, but I suspect it’s about the same for the vintage birds as well, someone with both a VP and a vintage Reverse or NR would need to confirm that.
Interestingly enough, all the birds I have from 1979 on (and I suspect the 76 as well) share the exact same bridge location, which is about 1/3 of a pickup width closer to the neck.
Conclusions - since the Thunderbird relaunch in the mid 1970’s it looks like the bridge pickup location has held steady, which is about one third of a pickup width further from the bridge.