Re: Nickel covered TB-4 vs TB-5 in a Japan 70`s Stratocaster
TB-5 Custom is a broader, more balanced sound. Deeper, gutsier punch. Great rhythm pickup, but good for leads and solid for cleans as well. Bit more of a hot PAF sort of sound, with ceramic low end, but much less of the harsh ceramic bite than most other ceramic pickups. I lean towards it more in thicker sounding guitars.
TB-4 JB is less tight, more towards screaming leads. Classic 80s metal pickup, but far more flexible than that. Blues through metal staple since it's introduction in the 70s. With high gain, prone to crazy beaming harmonics that are a blast for soloing.
I'd normally recommend trying the Custom, and if it's too bright, look into snagging an A8 magnet. With A8 it's warmer, not even a hint of ceramic highs. But keeps the beef, though slightly less deep bass it's still beyond other alnicos. Vintage metal tone that never was. Warm leads, punchy rhythms. Forum favorite for anything from blues to metal. Cleans and low gain improved over the stock Custom, more work to get a harsh thrash rhythm, but considerably improved lead tones. But magnet swapping is a bit more involved in a covered pickup, not sure you'll want to mess with that.
Could just as easily argue for the JB, though. When it works with a guitar, it's amazing.
How bright is the guitar? If it's particularly bright, I'd go for the JB first. The JB has a rep in some circles as a bright pickup, but it's actually craziest in the upper midrange. As long as the guitar doesn't exacerbate that, bright guitars usually just extend the high end and make it a more balanced pickup. Which is why it's popular in all-maple guitars that are horrifically bright with many other pickups!
