Need Permalink Assistance for Blog Split

Last week, I exported my blog’s contents and imported selected posts w/comments into a new blog. I plan to delete those selected posts from the original blog. The goal is to take an existing blog and split off topics into a new blog. The split went well; that’s not the problem.

The problem is that search engines point to the posts on the old site. I want to delete those posts. While I don’t mind users getting a 404 error message, I’d like that message to point them to the correct location.

I thought ahead. I used the same permalink structure on the old site as the new one. (The standard date-based format.) So the post on the new site has the exact same URL as it had on the old one — but with a different domain name.

Keep in mind here that I’m not deleting the old domain. I’m keeping it with the posts that were not moved to the new site. So this isn’t a simple instance of changing a domain name.

I am not a PHP programmer, however, I believe this can be done on the 404.php page using the the_permalink tag and some kind of parsing which is beyond my capabilities.

My idea is that when someone visits a page that has been deleted, the 404.php page appears. That page says (among other things) “You’re looking for a page that has been moved. The new address is:” followed by a link to the permalink with the domain name swapped out. The visitor clicks the link and, if the page is one of the moved pages, he get the right page on the new site. If it isn’t one of the moved pages, he gets another 404 on the new site.

I realize that I could simply add redirects to my .htaccess file. I’ve actually done this for about 20 posts and it works fine. However, there are 300 posts that will be deleted and I think that would be an unreasonable burden on the .htaccess file or server. Not to mention what a pain in the butt setting up all those redirect instructions are.

I know you guys are busy and I know it’s a bother to help individuals with tiny little problems that no one else is likely to have. But what is impossible for me to figure out might be child’s play to you. So I’m asking for your help.

Thanks.