Alternate victory cards can give rise to the following outcomes for passing a single standard VP card:
8 points from gardens by crossing a threshold (all gardens on the NV mat)
16 points from bumping up fairgrounds
8 points for bumping up silk roads
8 points for bumping up 8 dukes (gain a duchy only)
8 points for bumping up a vineyard (gain an action, like island)
So total possible swing from alternate VP is only 8+16+8+8 = 40 for a single card. One cannot get both a duchy & an action with a single card so you cannot get both the vineyard points and they duke points. With a 6 point swing for passing the duchy itself, that leaves us with 46 points moving. While massive, is not what the OP has in mind. The max swing from one card passing hands is 20 points for a colony, which makes it less than swapping a duchy with all dukes in play.
Passing a single VP alternate VP card have the following limitations:
Max values per card (note I'm assuming that the regular VP cards, including colony, can be used to make the distributions such that both players on right on the cusp for fairgrounds and silk roads):
Passing a garden: 24 point swing from silk roads & fairgrounds. This still leaves you needing a 610 cards in play (e.g. 310 per player) to make this hit a 85 point swing. I believe I remember there is no specified limit on treasures, so you could in theory setup with whatever you want and eventually get here.
Passing a fairground: This could swing up to 16 points for gardens and silk roads, this would then require you to have 175 unique cards in play per player; this would require gaining 155 cards from the black market per player.
Passing a vineyard: You can get a swing of 32 from gardens, fairgrounds, and silk roads. This leaves us needing to find 53 points to swing. That means we need 159 action cards. That leaves us with 8 kingdom stacks (bane) full of actions to exhaust 80 cards, this would require us to gain 79 actions from the black market deck assuming the vineyard was gained there as well. With only vineyards we could have 110 actions in play (bane) which would require gaining 145 actions out of the black market deck (and the vineyard itself).
I can see two ways of causing most of these point swings:
1. Masq with nothing in hand/draw & gain this card. This has the upshot of taking from one player & giving to the other. However, with vineyard only one player can have all those actions so it is pretty moot. If we don't want this to be a helpmate, then we can say that you played a bunch of cut purses on a hand of four coppers & his vineyard.
2. Swindle. If there is nothing in the supply of the correct price, you are just SoL and lose the VP card. So I swindle your only vineyard into nothing (I have exactly one swindler and one NV in my deck, everything else is VP & treasures on the NV mat) and poof go the points.