Set oven to 350°F (175°C). In a medium bowl, combine the cream cheese, mayonnaise, and 2 to 4 tbsp Thousand Island dressing, stirring until smooth.
Add the chopped pastrami or corned beef, sauerkraut, and shredded Swiss cheese, mixing until uniformly incorporated.
Move the mixture into a small baking dish or slow cooker and sprinkle an additional handful of Swiss cheese on top.
Baked Reuben dip: Place in the oven at 350°F (175°C) for 20 to 25 minutes, until heated through and bubbling. Crock pot Reuben dip: Transfer to a slow cooker and cook on LOW for 1 to 2 hours, stirring from time to time.
Optional: Garnish with diced pickles. Serve warm alongside your choice of dippers, such as vegetables, crackers, or bread slices.