You might be able to take your existing page layout and map it to wordpress using mod_rewrite. Something like:
Code:
RewriteEngine on
RewriteRule ^oldpagename.html$ /newpagename.html [R,L]
Depending on the number of pages you have, you could do a handwritten set of rules for the transition depending on how important it is to keep the old links. Granted, a very large site might end up having a large set of rules.