Searching Posts from different Table Prefix on one install

Hello,

We have multiple wordpress installs (4 of them) on a single database. Each install has its own wp_config.php file that sets
$table_prefix = ‘wp_’; //or what ever

What we want to do is that we want the other installs to show our Categories and POSTS from one site on all other tables, but still get look and feel and every other database selection from their own unique tables.

I tried creating a new template and then in top tried to RESET $table_prefix but didn’t work. Again, i only want to do this for certain pages within the other sites, not all or nothing.

Thanks in advance