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Hi there, From how you've described it, the risk isn't worth it.  If the current site/domain is associated with unethical linking practices and has received a penalty in the past, which is likely from what you've said, then you'd be associating the negativity of that site with the new one. I'd suggest rectifying the current site, improving the quality and making it a site that Google would want to include in it's index and rank for certain terms, then 301 that newly improved site rather than doing so in its current state. (Public PR is only updated 3 or 4 times per year usually and is a not even worth bothering taking any notice of, the various stats in SEOmoz Pro tools such as Domain Authority and Page Authority, plus MozTrust are much more meaningful figures of which to take notice of). Hope that helps, Regards Simon