Legacy URL in custom content field?

I caught wind that there may be a *native*, non-plugin, method for setting a legacy URL through a custom content field. Yes/No?

Why? : I have gone through the painful process of migrating a Drupal site over to WordPress. With 2K+ blog/post enteries, I want to retain the original URLs as a last-ditch reference before kicking out a 404. I do want to use WordPress’ standard perma-link capabilities as the old URLs are all over the place.

I really do not want to head down the .htaccess route as it can really bog things down given the number of rules. All in all, we will be migrating 17 sites from different content management systems.