In a dry large skillet, toast ancho peppers on both sides for about 2 minutes or until they crackle and just turn color, turning once halfway through cooking. (Be careful not to burn them; it will make the mole bitter.) Place anchos in a small bowl; cover with boiling water and let stand for 30 minutes to rehydrate. Drain, discarding water. Remove seeds; set anchos aside.
Heat oil in the same large skillet over medium heat. Add onion and garlic; sauté for about 5 minutes or until onion is tender. Stir in sunflower kernels, cinnamon, cumin seeds, and allspice; cook and stir for 3 to 4 minutes more or until mixture is very fragrant. Transfer mixture to a blender or food processor.
Add 1 1/2 cups broth, bread, tomato, chipotles and ancho peppers to the blender or food processor. Cover and blend or process until smooth, adding more broth if needed to thin the mixture.
Transfer the mixture to a large saucepan. Stir in the remaining broth, chocolate and 2 teaspoons sugar. Bring to a boil; reduce heat. Simmer, uncovered, for about 30 minutes or until desired consistency. Season to taste with salt, black pepper and additional sugar. Cover to keep warm.
Meanwhile, season meat with salt and black pepper. Arrange hot coals around a drip pan in a charcoal grill. Test for medium-high heat above pan. Place meat on the grill rack over the pan. Cover and grill for 30 to 35 minutes or until internal temperature registers 155°F on an instant-read thermometer. (For a gas grill, preheat grill. Reduce heat to medium-high. Adjust for indirect cooking. Grill as above.) Remove meat from grill. Cover with foil and let stand for 15 minutes. The temperature of the meat after standing should be 160°F. Slice into 1/2-inch slices.
Place meat slices on a serving platter. Top with mole sauce and sprinkle with pepitas