Mag swapping on the 59/Custom Hybrid is almost ridiculous. It's already tweaked and sounds great as-is. If anything, A2 might be cool or UOA5 would give it some vintage velvety softness, but all of the qualities it has going for it in stock form are what makes it great. If you want to put an A8 then why bother with the hybrid? You might as well get an Alt 8, PATB-2, or Crunch Lab or something. The Jazz MIGHT benefit from an A8, but it's such a powerful magnet that I doubt it will balance properly with any bridge. You would have to lower it so much that it will become almost useless. Then you would lose all that high end detail and balanced low end that makes the Jazz a great neck pickup.
Honestly, I think magnet swapping is becoming ridiculous. It's a nice option if you have a SPECIFIC, minor change in mind, but if you don't know exactly what you want to achieve, it equates to just time spent experimenting. The qualities of each pickup are already posted out there. I just imagine how a minor variance in output and tone matches with the tonal qualities of the magnet type and it always gives me pretty much an accurate idea of what I find when I do the swap. I haven't really been surprised yet.
These days, it's the amp + speakers mostly. Most pickups are essentially a matter of output, feel and basic underlying EQ. Some pickups, like certain Dimarzios, have rather unique sounds, but most pickups sound similar except with minor EQ differences. I look at pickups is kind of the link between me and the amp rather than a major part of the tone. You can swap magnets and tweak all you like, and you might just get lucky, but most of the time you have to have a specific purpose in mind or your pickups need to be designed with that certain magnet in mind perhaps.
I'm just being honest here because I think mag swapping on the 59/Custom Hybrid is pretty much a waste of time. Get yourself one of those roughcast A2 magnets and you will have a little more thickness, a little less top end brightness, but you are going to lose a little output. A polished A2 will be slightly more powerful and give you the same effect but not exactly the same vintage softness. UOA5 will probably work perfect tonally, but he 59/Custom already feels loose to me and wouldn't feel right with UOA5. Plus, you will lose a little power. Ceramic will definitely be thicker and more powerful, but I don't think it will tame the high end or add any mids. A8 will be thick and warm, but you will lose a lot of things that make it a cool pickup. It's too powerful and you won't have the dynamics and all that. You might as well get one of those Liberators and turn it into an active pickup or something.
