[development] Drupal search, group by content type

Is there an easy way to change the keyword search results so they are ordered by content types, then by score? I want to 3 of my content types to always appear in the results first (in an order I determine) ordered by score. Then all other results to appear after by score DESC. Seems that just by modifying the $sort_parameters of the do_search() function would do it, but the order of the results I'm getting doesn't seem like it is having any effect (maybe due to the pager too). Drupal 6.