BigDave - 12:58 am on Apr 28, 2004 (gmt 0)

If you really think that it is a filter or penalty (which I personally doubt) then you should definitely avoid doing a 301 to the new site. And you never know, Google may tweak their algo next month and those sites may shoot back up to the top.

You implied in your original message that your client might be looking for long lasting results. Well, long lasting results take a while to build, so don't take shortcuts. Make this the large autonomous site that is squeeky clean.