If you want to get technical, the 1973 side covers had a mid-year change. You don't want to put a late 73 cover on your 72. Read all about it here:A quick question regarding side covers. Will '73 covers fit a '72? I know there is a little difference in them regarding the trim mounting holes and the badges are different. Other than that do they mount the same?
https://www.xs650.com/threads/alternate-1973-side-cover-why.54732/