[jnr]

Posted this elsewhere in a response but I thought I'd post it as a topic because it seems to come up and I found the simple answer.

With a assist from Jake Bunce of the vBulletin team, who suggested I use the RewriteEngine, I tracked down the solution. I modified the code I found at http://www.webmasterworld.com/forum92/1917.htm. Here's an example of how to do it:

To redirect defunct link
http://www.greenmachines.net/forumdisplay.php?f=16

to
http://www.greenmachines.net/forumdisplay.php?f=31

put this in your .htaccess file:

Options +FollowSymlinks
RewriteEngine on
RewriteCond %{QUERY_STRING} ^f=16$ 
RewriteRule ^forumdisplay\.php$ http://www.greenmachines.net/forumdisplay.php?f=31 [R=301,L]