tedster - 6:29 pm on Apr 7, 2009 (gmt 0)

If you change content and Whois and DNS - then Google very well may "reset" the domain to zero and give it a total fresh start.

I can try, but it is unlikely that I can keep the old sites. The domains aren't worth much on their own

Then I would say don't pay too much for just the domain names. If you're not going to be purchasing and maintiaining the existing business, then Google does not want to rate your new "business" as if it were the previous one, even though it's at the same address.