How long should I cook two 8 pound fully cooked half hams in one pan together?

Put them in a pan with the cut-side down. You can use a cookie sheet if you don't have a big pan. Just cover the cookie sheet with aluminum foil. If you have a big pan, add two cans of Coke. Bake them at 350 degrees. I don't know how long, since you didn't say how muvch they weigh.