A client that I worked with on another project has approached me asking if I can handle the transition from his old website to his new website. He already had the new website designed and the URL structure is completely different than the old one. Normally this would not be a problem, just 301 redirect each page to the new page. However, this client has COMPLETELY redone his website from the ground up including navigation, pages and page content.
The old website has been around for 8 years and is ranking for some good keywords. The reason he decided to build the new site is because the URL of his old domain is very long and for whatever reason he didn't like it (I'm assuming this would be misspellings of people trying to get back to his website and long email addresses, but he didn't clarify).
I have never dealt with such a drastic change before and wanted the SEOMoz community input on the best way to pass authority/link juice from the old domain to the new one.
Thanks in advance for your help.