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No problem, as long as you still have links in. Of course these old links will be from 'off theme' sites, so IMHO may count for less. If they have anchor text such as 'hotels in Scotland' then your car site will not benefit from this, and it is unhelpful to a user. But as far as google is concerned, the pr will still be there and you are up and running. Get new links in or modify existing ones where possible to be back on a car theme. Also try and use the same file names, as these will already be indexed and floating around the web, with links possibly going directly to them. They may have found there way into inktomi or other engines, so don't loose them.