I recently bought a 67 Convertible which, apart from the floorpan problem has only a little rust. One area are the corners of the brace and panel behind the rear window. Is this a common problem, what causes it and is there anything that needs to be done to protect this area from rust in the future? Where can I get the correct parts to replace the rusty ones? The top panel seems to be available for 64-66 models only - or is this used for later models too? Thanks for your help.