Best bet is to either drill, dremel, or grind the heads off the bolts. With a dremel or small grinder you should be able to get enough of the head gone to pop off the rest without screwing up your chrome. You should be able to pull them out from the inside along with the metal pieces they screw in to. Then take it to your vise and grab the remaining length of bolt. With a little persuasion or heat you should be able to spin them out. It's always a bitch doing it on the bike.