I can offer some info on the USA JB-2, but not the Tribute version. Been a JB-2 fan since 2002, have had at least eight of them, still have two.
First production year was 2001, and they were first displayed at 2002 Winter NAMM. That was the first, and only year it was available with an optional solid birdseye maple neck. What I discovered with them is that they can sound very different, one from another, even when built with the same wood combos and same strings. Some had a nice lively snap, some were totally blah and non-descript.
I suspect there may have been some variances in the s/c pickups, not sure. I asked a G&L dealer if the pickups were made in-house like the MFD's were, or out sourced. Never got an answer.
OTOH, the more lively sounding ones were noticeably more microphonic, picking up every little sonic detail, even the faint squeaking noise from a leather strap rubbing against the body. Those were the ones I liked the most because along with the unwanted extraneous little noises (spring ping renders a JB-2 virtually unplayable), every playing nuance was also highlighted, which means a more expressive instrument. For my tastes, the JB-2 really likes flats, especially TI's and Labella Deep Talkers.
Only two of mine weighed in at just above 9lbs. The others all came in at 8 1/2 lbs, or slightly less, if that's a concern. All mine came with the default #8 neck, which most of us fans think is pretty comfy.
In the early days there were lots of JB-2's floating around with figured tops. There were great deals to be had on slightly used ones early on, as G&L had neglected to install the all-important little rubber dampeners inside the pickup mounting springs on all their basses during that time. Spring ping on a JB-2 is intolerable. On an MFD equipped bass, not so noticeable. Hence the great JB-2 deals popping up.
Hope this helps, if I think of anything else, or if you'd like to see pics, I'l post. Cheers.
Edit: The USA pickups are different lengths, so may sound different than the Tribute ones.