Here is my issue. We are changing our linking structure from

www.site.com/trailer/movie-title/video-title

to just

www.site.com/movie-title/video-title

Obviously I want to 301 redirect (using nginx/mod_rewrite), but do not know if I should care about poorly/incorrectly written incoming links. Such as a site that miswrites our url as

/trailer/movie-title/video-titlez

They accidinatelly put a z on the back of the video title, and we'd respond with a 404 response when the page is open. Now, with the mod_rewrite, I would be 301 redirecting this bad url to the PHP file that analyzes, and then gives the 404 response.

Is this okay way to do it? I've been told I don't need to worry about what SEs like Google thinks of 301 to 404 since the page was a longtime 404 anyway.

The only other way to do it is leave a PHP file at the old url address and have it check the database and confirm the link is correct before forwarding on to the proper url if item exists or posting 404 response if not, which unfortunately means the 301 forwarding would mean my database would then need to effectively be checked twice if item exists, since the new url and PHP attached would double-confirm.

Seeking feedback on this.

Thanks!
Ryan