Heat oven to 400. Poke several holes in each potato, place in oven. Cook 1 hr, or until soft. Remove potatoes from oven. Reduce oven temp to 350.
Slice each potato in 1/2 lengthwise. Scoop out the flesh and place in a bowl. Place potato skins on a lg baking sheet. Add butter to potato flesh in bowl. Mash w/ a masher. Add 1/3 cup sour cream, light cream, salt and pepper. Beat until smooth.
Fill potato skins w/ mashed potato. Sprinkle potato skins w/ cheese. Bake 15 mins, remove from oven. In small bowl, whisk ranch dressing mix, 1/4 cup sour cream, mayonnaise and milk until smooth. Sprinkle each potato w/ bacon and green onion. Drizzle w/ dressing.