I like how this looks, as if it were tailor made to beat thresh. What's it matchup like for other big decks in the format, like landstill or goblins (yes I know goblins has fallen from it's throne but it still shows up) or combo like SI or Iggy Pop?
I can test it out a bit. In all honesty, I believe the Urzatron is better just because with all three it generates 7 mana. With posts, the closest you can get is 6 (unless you're playing your 4th post after tapping one for mana).
Unfortunately, back when I played it last, Tooth and Nail wasn't able to do very well in Legacy, mostly because Goblins and Solidarity were too fast for it, and decks like Landstill and Threshold were running around. Now, Goblins isn't as format defining as it was, and Solidarity can't exactly survive well because of the other control, but there are faster combo decks, mostly SI and Warrens Belcher that just crush Tooth and Nail. Also, most counterspells will stop you, and a well timed Swords To Plowshares will slow you down quite a bit.
I don't have a decklist, but I can tell you general things that I've seen in the deck. Usually, the win is a resolved Tooth and Nail to grab Mephidross Vampire and Triskelion or Kiki Jiki, Mirror Breaker and Sky Hussar. The Urzatron is a good way to generate the mana to cast it, so also plan on using Sylvan Scrying to grab what you need. Sakura Tribe Elder is also an excelent way to grab extra lands, and to help you survive the early game.
unfortunately, its just not as good against affinity, since it can get its creatures up to lethal usually by turn 4 undisrupted (or at least the Green build can) Cranial Plating gives a great way to get around it, and post board, there still Pithing Needle.
Blinkmoth Well was only used in extended back when Scepter-Chant was running rampant. Since it is basically non-existant in legacy, you shouldn't have to worry about it.
From what it looks like, your deck bends over to Pithing Needle. I do agree with cy31791, where swords to plowshares should be an auto-include, but contrary to his beliefs on stifle, I believe it should remain. If you decline to run wastelands, this can be nearly as good, or even better in some cases, given that most decks will be running fetchlands. It also makes storm combo cry a little bit, and other than that, is just great for most matchups. Also, vanishing and echo end up hurting quite a bit in a long game.
Don't forget the universal sideboard card: Pithing Needle. That'll shut down your ravager, atog and cranial plating. Also, fling can be risky if playing against blue. Since the sacrificing is an additional cost, it can cost you a giant creature for potentially no effect. Tarmogoyf's have been seen in the green build, but for a more budgeted version, stick to red.
Chaotic Thinking UR
Sorcery
Flip a coin. If you win the flip, draw three cards. If you lose the flip, each opponent draws three cards.
Unfortunately, back when I played it last, Tooth and Nail wasn't able to do very well in Legacy, mostly because Goblins and Solidarity were too fast for it, and decks like Landstill and Threshold were running around. Now, Goblins isn't as format defining as it was, and Solidarity can't exactly survive well because of the other control, but there are faster combo decks, mostly SI and Warrens Belcher that just crush Tooth and Nail. Also, most counterspells will stop you, and a well timed Swords To Plowshares will slow you down quite a bit.