Add the chilies a medium mixing bowl and top with hot water. Let sit until the chilies have softened, about 10 minutes. Remove the chilies and discard the water.
Add the reconstituted chilies, onion, garlic, oregano, cumin, cloves, cinnamon, pineapple juice, orange juice and vinegar to a blender. Blend until the mixture is puréed.
Season the pork on all sides with kosher salt. Heat a large (7.25-quart) Dutch oven over medium heat, add the oil and heat through. Add the pieces of pork, working in batches and brown on all sides about 6 minutes. Set aside.
Add the chicken stock to the pot to deglaze the bottom. Return the browned pork to the Dutch oven and pour the mixture over the top. Add the pineapple.
Bring the mixture to a simmer over medium heat. Move the Dutch oven to the oven and cook until the mixture is fork tender, about 2½ hours, rotating the meat halfway through cooking.
Remove the meat, from the braising liquid and let cool. Use two forks to shred the meat or chop the meat then return to the braising liquid.
For serving:
In a small bowl stir together the pineapple, onion, cilantro and lime juice. Season the mixture with salt and set aside.
Heat a large skillet or griddle over medium heat and put two tortillas on top of each other, then warm the tortillas on both sides. Repeat with remaining tortillas.
Use tongs to place about ¼ cup of meat on each tortillas. Top with a spoonful of pineapple, onion cilantro mixture and Avocado-tomatillo salsa verde (optional).