Heat the oven to 300 degrees F.
Place the oil, onion and garlic in a Dutch oven. Sprinkle the pork with salt and pepper and add to the pot.
In a pitcher, combine the pineapple juice, grated ginger, chicken stock, wine, brown sugar, soy sauce and some salt and pepper. Pour over the pork. Cover and place in the oven. Cook until the pork is easily shredded with a fork, 2 1/2 to 3 hours.
Remove the pork from the pot and strain the sauce using a de-greaser to separate the fat. (If you don't have a degreaser, strain the cooking liquid into a shallow pot and let cool. Refrigerate, then take the cooled sauce from the fridge and skim off the fat.)
Shred the pork using two forks and put it in a bowl. Add some strained sauce to the pork; start with 3/4 cup and increase until the pork mixture reaches the desired consistency for your tacos.
For the tacos: Warm the tortillas on the grill.
Fill with the shredded pork mixture and top with fixin's.