Cook noodles in large pot of boiling salted water until almost tender but still firm to bite. Drain well, then return to pot.
Meanwhile, sprinkle pork with salt, pepper, and five-spice powder. Heat 1 tablespoon oil in medium skillet over high heat. Add pork and stir-fry until cooked through, about 2 minutes. Add remaining 2 tablespoons oil, soy sauce, and vinegar; stir 30 seconds.
Add pork, green onions, and radishes to noodles and toss to combine. Season to taste with salt and pepper.
