We have 4 years old HTML website of a good quality with a lot of content and high quality backlinks but bad CMS. So for a long time already we are looking for solution to add Wordpress functionality to our site without losing SERPs. After googling for possible solutions it seems there are three of them: 1. Convert website to wordpress 2. Modify WP plugins to work with existing CMS 3. Integrate wordpress into existing website We are currently stuck with the first option for about a year - big volume of work, high cost, difficulties to recreate old URLs structure on Wordpress. I wonder if Wordpress installation into sub-directory of our website can work... Basically we would like to keep old content as it is and continue with new content on Wordpress. What could be the most time/cost/SERPs effective solution? Any advice will be appreciated.