For the chicken al pastor: Put the orange juice, vinegar, chile powder, honey, cumin, oregano, garlic, chipotles, onion and 1 teaspoon salt in a blender. Pulse several times until chunky. Add the oil and pulse to make a smooth marinade. Pour the marinade into a large resealable plastic bag and add the chicken. Marinate in the refrigerator at least 2 hours and up to 8 hours.
Remove all but the bottom oven rack and preheat the oven to 400 degrees F.
Cut the top off the pineapple and reserve. Cut off the peel from the pineapple. Cut a 1-inch slice off the top of the peeled pineapple, chop and reserve for garnish. Slice the remaining pineapple in half. Put the bottom of the pineapple on a rimmed baking sheet and insert a long skewer, pointy side up.
Drain the chicken from the marinade and pat dry. Season with salt and drizzle with a little vegetable oil.
Thread the chicken on top of the pineapple, then top with the top half of the pineapple. Transfer to the bottom oven rack and roast until the chicken is tender and caramelized on the edges and the internal temperature measures 165 degrees F on an instant-read thermometer, about 1 1/2 hours. Transfer the chicken to a cutting board and let rest 15 minutes.
For the spicy cabbage slaw: While the chicken roasts, make the slaw. Whisk together the orange juice, lime juice, honey and 1/2 teaspoon salt in a large bowl. Stir in the jalapenos and brine. Whisk in the oil in a slow stream to make a smooth dressing. Add the cabbage, cilantro and red onion and toss well. Refrigerate until the chicken is done.
For the tacos: Heat the taco shells according to the package directions.
Put the reserved pineapple top on the chicken and pineapple stack, pushing it through the skewer. This will allow you to hold the stack steady while you cut the chicken and pineapple.
Use a sharp knife to make thin vertical slices.
Serve the sliced chicken and slaw in the taco shells with toppings of your choice. Finish with a squeeze of lime.