Place steak on a plate, pat dry and sprinkle generously with salt and pepper on both sides. Let sit in the fridge while you make the corn salsa and cilantro sauce.
For the corn salsa, heat a large pot filled halfway with water over high heat until boiling. Add corn, cover, bring back to a boil, then lightly boil for 3-5 minutes. Remove corn from pot with tongs and let cool slightly. Once corn is cool enough to handle, slice the corn off the cobs into a medium bowl. Toss corn with red onion, cilantro, lime juice and olive oil. Add salt and pepper to taste. Refrigerate.
Make the cilantro sauce - in a food processor, combine cilantro, sour cream, garlic, lime juice, salt and pepper. Process until smooth. Adjust seasoning if needed. Poor into a small bowl. Refrigerate.
Preheat grill to high heat. Clean and oil the grates.
Pat scallops dry then brush lightly with oil, sprinkle lightly with salt and pepper.
Reduce grill heat to medium high. Add the steak to the grill and grill until desired doneness, flipping after 3-4 minutes. USDA Food Safety states that steaks should be cooked to a minimum of 145 degrees F with a 3 min rest, as measured with a meat thermometer in the thickest part of the steak, away from the bone or fat. Remove steak from the grill and let rest.
While the steak is resting. Add scallops to the grill and cook 2-3 minutes, flip, then cook until just opaque, another 1-2 minutes. Don’t overcook. Remove from grill.
Slice steak thinly against the grain. Cut scallops in half.
Assemble tacos by adding steak and scallops to a warmed tortilla. Generously top with corn salsa. Drizzle with cilantro sauce. Serve with lime wedges and remaining corn salsa.