I have 20+ domains all parked onto one domain. There is one index.php that shows a different set of text depending on what domain is being viewed. I am now seeing many 404 errors since some of these pages once had content. Can I make the 404.shtml a 301 redirect? If so how can I do it so that it points to the right domain? The 404.shtml is used by all of the domains. So there an easy way to do this? I think I can just tell it to redirect to / or /index.php but how do I cover all the other pages/dirs that no longer exist?
If you do that you will just confuse your users. Don't do it, better put up a link and point them to the right location.
I don't understand what your problem is, but it seems that you just need to redirect some specific old pages to the new ones, why would you want to redirect the 404 page?
have gave up on a bunch of domains. They are now parked. With the parking places I use they dont offer their nameservers just a url to forward to. Right now only people going to the domain.com get sent to them the rest get a 404. I want to redirect ALL traffic to them.