1. In a small bowl, combine chili powder, cumin, oregano, salt and pepper. Season the pork loin with spice mixture, rubbing it thoroughly on all sides.
2. Place pork loin, garlic, onions, orange juice and lime juice into the slow cooker.
3. Cover and cook on low heat for 8 hours.
4. Remove pork from the slow cooker and shred the meat before returning to the pot with juices. Season with salt and keep warm for 30 additional minutes.
5. We took the tortillas and heated them in a pan and melted the cheese on top. Then added lettuce, pork, tomatoes, sour cream and squeezed lime juice to taste. They were delicious!