Lots of hum-cancelling J pickups out there to choose from - Seymour Duncan, Nordstrand, Fralin and others. I've got SD Area Js in my JB-62M and they sound very close to vintage single coils. Adding shielding to the pickup and control cavities can help to reduce hum (I use graphite paint which is easier to apply than copper foil). Preamp may add hiss but unlikely to add hum unless something is wrong with it (eg. a grounding issue).