Depending on what you need the fellow who used to make 49-51 Merc structural sheet metal parts for Green Mountain Parts still has parts for sale on eday, ie, outer rockers, inner rockers, floors. Maybe he would make you a trunk floor. Green Mountain made mine in 1996 and it was very high quality out of 16 ga.
Bill's a guy that specialize in 49-51 Merc parts. He's in CA and knows what the parts are worth but they are usually really clean and rust free. He also has repro parts. Here's a link: http://www.papkeent.com/ Good luck with your project. Mike www.customikes.com