22357 Re-writing 120 articles

I am looking for an experienced content writer to re-write some articles. I am hoping this can work out to be a monthly thing. I recieve 120-160 articles per month... Each article is approx 400-500 words in length, well written, and researched. What I have is article sets of 40. Here is what I need. I want someone that can re-write these articles so that they are unique. By changing the headline, re-writing the 1st & 2nd paragraphs, the last paragraph and making some changes to the middle paragraphs... (i.e. create a list of items etc.) I also want to increase the keyword density of each article. By this I mean increasing the number of times the keyword appears in the article. All in all these articles are coming from a membership site and many people recieve them I want them to be original so that the search engines don't penalise me for duplicate content. For the right person this is a monthly job where I will supply 80-120 articles each month. I will pay either on a 40 article basis, or once monthly for the amount of content. Please ask any questions. This Project is for Re-writing 120 Aricles.