You could drill out the threaded and unthreaded hole opposite it to fit your bolt size - as long as the collar is high enough. The real issue with this is will the collar height align with the rudder position you want with the load bearing washer you put underneath it. You may have to do a custom thickness on the washer.

If your boat is in salt water that aluminum collar may be unmoveable. Be prepared to cut or grind it away.