Thanks Joe! I guessed right on the spool pin. It felt smooth when I stuck a toothpick down that hole and ran it up the sides. I am assuming I could order the tap in spool pin with the thread guide holes?
Interestingly, the belt and bobbin tire winder look fairly new. I am going to look at the belt again later (with a flashlight) to be sure I am not missing any cracking or the like. But thank you for the information on which belt yours uses. I hadn't tried to measure mine yet.