Combine the olive oil, lime juice, orange juice, shallot, garlic, crushed red pepper and 1/2 cup cilantro in a mixing bowl. Divide the mixture evenly into 2 large zip-top bags. Seal one of the bags and refrigerate for use later. Add the skirt steak to the remaining bag, seal and refrigerate. Let marinate for at least 2 hours and up to 4 hours.
Once the steak has about half an hour left to marinate, remove the shrimp from the fridge and skewer onto two side-by-side skewers to prevent the shrimp spinning when flipped on the grill.
Brush the reserved marinade onto both sides of the skewers with a pastry brush, and place the skewered shrimp onto a plate. Refrigerate for 15 minutes.
Bring your grill or grill pan to high heat. Remove the shrimp and steak from the fridge and use tongs to transfer the steak from the marinade.
Sprinkle both sides of the shrimp and steak with a pinch of salt and place onto the grill. Cook both for about 4 minutes on each side, until the steak has started to char and the shrimp have cooked through. You may find the steak needs a minute or so longer than the shrimp, depending on how thick the cut of steak is. Remove both from the grill, and let rest for 10 minutes.
Make the pico de gallo.
Cut the steak into several 4”-long cross-section along the grain. Then cut each cross-section into 3 to 4 strips against the grain, severing the long muscle fibers and making the steak easy to chew.
Assemble the tacos by starting with steak, followed by the shrimp, pico de gallo, sour cream and cilantro.
*Pico de gallo: Combine 1 medium tomato, 1 small finely chopped red onion, kernels from 1 cob sweet corn, 1/4 cup lightly packed cilantro and 1 tbsp lime juice. Season to taste with salt and pepper.