Mix chili powder, garlic, lime juice, 3 Tbs. olive oil and cumin in a large bowl to form a paste. Add the beef and mix till coated. Refrigerate 24 hours, stirring occasionally. Position rack in lower third of oven and preheat to 180ºC . Combine marinated beef, canned tomatoes, broth and beer in a Dutch oven. Bring to boil over high heat. Cover, transfer to oven and bake for 45 mins. Uncover and continue baking until beef is tender, about 45 minutes more. Cool, shred beef and return to cooking liquid. Cover and refrigerate overnight. Heat 3 Tbs. oil in heavy skillet over medium-low heat. Add onion and jalapenos then cover and cook until onion is tender and lightly browned, stirring occasionally, about 15 mins. Strain beef cooking liquid into skillet, Bring to a boil. Reduce heat and simmer uncovered until sauce is thickened and reduced to half cup, stirring occasionally, about 50 mins. Mix in beef. (Can be preparted 1 day in advance and refrigerated). Add corn, olives, and pimentos and stir over medium heat until just heated through, about 5 minutes. Season with salt and pepper to taste. To assemble: Half fill taco shells with beef mixture. Top with cheese, lettuce and chopped tomatoes. Serve immediately, passing salsa and sour cream separately. Note: The same filling also works in chimichangas and enchiladas, and is delicious spooned over toasted hamburger rolls. It can also be frozen.