i dont think there is a fundamental turn in vintage like modern, the biggest reason for this imho is that there is much varience in games, and that there is a wide variety of deck, from the turn one decks to the turn 20 decks, and the simple fact you can win out of no where, so in my opinion there is no fundamental turn.
I agree with letseeker that the Fundamental Turn concept doesn't really make sense in Vintage (or any format with Force of Will and Mental Misstep so prevalent).
First of all, it's not totally clear to me what it even means for a format to have a fundamental turn: in Zvi's original definition of the fundamental turn (see http://www.starcitygames.com/article/3688_Clear-The-Land-And-The-Fundamental-Turn.html) the fundamental turn is a property of decks, not of formats.
In this context one can speak of the FT of combo decks like Storm or Dredge, where the FT is the average turn they kill a goldfish; these decks have a FT between 2 and 3. But I think this is the only sense in which the FT concept makes sense in Vintage.
One could try to do something similar for aggro decks, but since all Vintage aggro decks contain a strong control or disruption component, just looking at the goldfish turn is not especially meaningful.
For control decks the original FT was the turn in which the deck could sweep away all of the opposing threats and take control of the game. Vintage control decks have no sweepers (other than sideboard answers like Supreme Verdict or Hurkyl's Recall) and instead start interacting with other decks immediately via free counters, and from turn one have access to potent answer spells like Swords to Plowshares, Nature's Claim, and Pyroblast. So one could argue the FT for Vintage control decks is 0, but this is not a meaningful number in my view.
One can define the fundamental turn as "the turn by which you must have won or disrupted your opponent or else you will lose the game." This is a less nuanced definition than Zvi originally proposed, and I would agree with Duck that by Turn 2 you had better have some way of stopping Dredge or Storm.
I pretty much agree with @evouga: it's not the format who sets the fundamental turn, but the chosen deck. Moreso, there are decks with a fundamental turn, but others that don't. In fact, most vintage decks don't have a fundamental turn other than 0/1. Aggro decks have it, but since most vintage aggro decks rely on some mana denial, that fundamental turn can be increased.
Besides the fact that some vintage decks can win in one turn "unexpectedly" makes that fundamental turn a liability. Even with mentor and 4 tokens in play with active fow and gush, passing the turn can mean defeat against an opponent with no hand.