One difference between IL and MO is the Coaching box. If I remember correctly IL has a 14 ft box and MO is larger possibly 28ft line to baseline. So if you are officiating in MO you shouldn't have any problems with this. Other than that everything else should be the same.

I used to officiate in MO am now in IN and also registered in IL. From what I have seen between MO and IL there are many differences except that IL seems to want the officials to be stricter on uniform issues and the coaches box.