I have a client who has a 14+ year old site, ranked fairly well in the search engines, but his site isn't converting well (to say the least). He wants to update to web 2.0 (probabaly wordpress), and I told him I would check and see exactly what needs to be done. I've heard about people rebuilding their sites and losing all domain age. I don't want that to happen to him. What is the best way to upgrade an old site to a new site without losing any authority?