All Windsor engines come from the factory with that washer. It's not an
oil slinger. The goal is to keep pressurized
oil off of the seal, and helps prevent leaks.
I have never found one in any catalog. Not even sure you could get it from the Ford dealer. I have only seen one a couple of times over the years. Only when I'm taking apart an original factory assembly that no one has touched before.
This is a picture of an old Dodge motor. Same concept.
Without it, you can sometimes run in to spacing problems at the front of the balancer.