One of GT's main selling points is that it's low-magic. It may not be particularly appropriate for a straight D&D port.
And I'd suggest reverse engineering, and then adapting where inappropriate. Urban Arcana gives a list of class equivalents for the D&D core classes
Code:
Barbarian Thrasher
Bard Personality or Negotiator
Cleric Acolyte, then Ecclesiarch
Druid Wildlord and Mystic
Firghter Archaic Weaponsmaster
Monk Martial Artist
Paladin Archaic Weaponsmaster, then Holy Knight
Ranger Wildlord
Rogue Infiltrator
Sorcerer Mage, then Archmage
Wizard Mage, then Archmage
Of course, some stuff on this list is problematic.
Neither the Personality nor the Negotiator is a particularly good fit for the bard. Glamourist is probably the best AdC to represent a bard, as it's got much better synergy with the inspiration talents of the Charismatic base class. Even then, the Glamourist only has a couple of spell-like abilities.
The Tierra Viejo website suggests that spellcasting bards are pretty rare, though, so that may be a bonus. And it wouldn't be to hard for bards to pick up a few levels of mage or sorcerer for spellcasting ability (or even telepath if you want to include psionics). Still, there isn't yet and advanced class that really captures the spirit of the bard, so this is the biggest candidate for an entirely new AdC.
the Cloistered/Martial divide for Tierra Viejo is probably best represented by the base classes chosen by prospective clerics. (for instance, Smart/Accolyte or Dedicated/Accolyte for cloistered, Strong/Accolyte or Tough/Accolyte for martial). The elven priests might be best represented via new AdCs or PrCs.
The list above predates the Shaman from D20 Past, a much better fit for the Druid.
Archaic Weaponsmaster works as a generic D&D fighter, but so do several other classes from a variety of sources. Don't limit yourself.
The Martial Artist is a lot less flavorful and mystic than the D&D monk. Given the Eurocentric nature of TV, however, that's probably a good thing here.
Holy Knight is a PrC, so you can't get any paladin-like powers until level 9 at the earliest. You might consider adapting the Purifier from d20 Future
As an alternative to the Wildlord, you could combine a few levels of Shaman with a martially focused Base or Advanced Class for your ranger build.
D20 Past's Gangster makes a good rogue if your primary goal is sneak attack
See Comments on Druid. The d20 Past Sorcerer makes a better sorcerer than the Mage.
As for the 30 or so PrCs, some might be easily adapted into AdCs or modern PrCs, Others translated into their Modern/Arcana/Future/Past/Apocalyptic equivalents, and still others just ignored entirely. I'd have read the the things and gone into greater detail, but I should have gone to bed two hours ago.
Night.
