Place pork roast in large stockpot. Add pintos, tomatoes, chiles, onion, garlic, oregano, chili powder, cumin, salt, pepper, and enough water to cover. Bring to a boil and lower to a gentle simmer. Cover and slowly cook 3 hours; remove meat and set aside to cool. Continue cooking uncovered until beans are tender, another 2 hours, stirring occasionally.
Meanwhile, remove cooled meat from bone, and shred or pull off in bite-size pieces. Discard bone and fat. Return to pot and cook 1 hour longer. Stir often and add more water when necessary to thin slightly. (Chalupas should have the consistency of stew).
Serve hot in bowls, with corn chips on the bottom, a ladle of chalupas, and pile on condiments of your choice. It will store well in the refrigerator for up to 1 week.
This recipe was provided by a chef, restaurant or culinary professional. It has not been tested for home use.