I don't remember it was a few years ago. I have been searching their site just now and do not see any 4 hole mounts listed. Maybe they do not carry them anymore. Keep us posted on your progress I'm enjoying the project. Motorcycle and harley shops also might have those to convert a trailer for tie downs. Those would be heavy duty, street bikes are heavy. For those Santa Anna wind days You could swing by parts counter , if one is near.