This is actually one thing boonex did do a good job with. I haven't verified them all but they work good for me.

On:
http://www.boonex.com/trac/dolphin/wiki/6.1.6to7.0

You want to make sure you pay attention and understand this part:
IMPORTANT
To make sure you are not banned by search engines and save all old links from Dolphin 6.1.6, do the following:

Add these modrewrite rules to your .htaccess file:

Rewrite rules here
and here
and here
etc.

Everything there is what will rewrite see more your old d6.1 links to 7x and they are permanent redirects like 301's which mean if you have any rank already google will pass it along and forward it to your new 7x links.

Make sure you understand them, they are not the clearest instructions in the world for someone not familiar with how permanent redirects work.

They should be added in addition to the standard d7 .htaccess file (yoursite.com/.htaccess). You need both the standard .htaccess file in the download and these additional ones if upgrading.

If you are not upgrading from d6.1x then you don't have to worry about this.