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Such site must still exist in the google cache to maintain pr. In order to complete the process -  rebuild the old site with the entire content from the cache . And you should be ok.

Here this one is interetsing also, not that matt nver says the statment is not true. http://www.youtube.com/watch?v=DnfM_szmDh0

The most important factor is to ensure only one URL is available for each page. You should not present the same page through both the /index.html and / URLs. Pick one. My strong preference is to use the simple / URL as "index.html" does not offer any value to users nor search engines. It just makes the URL longer and more cluttered. I'm sure Google knows that these are the same pages and does not consider them as duplicate ... Not true. On your site you may choose to offer the same content via /index.html and /, but another site could choose to present completely different content on those pages. You are offering two unique URLs, your content is duplicated and that can cause multiple issues. Duplicate content is an issue and a division of your links is another issue. The simple fix is to design your site from the beginning to only offer a / page and not a index.html page. If you have an existing site where this is an issue, use the 301 redirect to fix the problem.