I know they have different ids, this is done in the template. You would want to change $userinfo to $bbuserinfo, but this is from the template:
HTML Code:
<tr>
<td><a href="search.php?$session[sessionurl]do=finduser&u=$userinfo[userid]" rel="nofollow"><phrase 1="$userinfo[username]">$vbphrase[find_all_posts_by_x]</phrase></a></td>
</tr>
<tr>
<td><a href="search.php?$session[sessionurl]do=finduser&u=$userinfo[userid]&starteronly=1" rel="nofollow"><phrase 1="$userinfo[username]">$vbphrase[find_all_threads_started_by_x]</phrase></a></td>
</tr>