I only play Thunderbirds, both from the 70's and post '88 production. They're quite different in how they sound....The pick ups are completely different between those two variations of them....along with neck profile and size of the headstock. Classic versions are all 9ply neck thru construction, the now discontinued "studio" is a set neck instrument.
I've owned an Epi 'Bird too, not a bad bass for the $$$....however it's NOTHING like any Gibson for tone. The only thing that's the same is their body shape, all the materials used ( neck, pickups, bridge, body wood, bolt neck vs. neck thru) make them very different basses.
If you don't want to spend the big $$$ for Gibson I'd look at a Greco 'Bird, they're Japanese production very nice quality, set neck basses. I own one and really like it.
In this photo the 76's have chrome hardware, post '88's are black, I used to own Fenders, Musicmann and Rics....Now just 'Birds, for Rock with a pick they're great basses.
Here's my single pick up Greco 'Bird, @ $750.00 a great bass!