Have a Ford manual around but not scanned at the moment that shows how Ford suggested. But another option is from the text of a member (Pat) here that was working on an article for the Library about rebuilding the Thermactor pumps and below is what he found that worked for him. Sure he would be happy his information helping others. Thanks Pat
More people have ruined perfectly good fans just by prying it off with a screw driver. These fans are forty odd years old and like our bones they are very brittle and crack very easy.
Here’s the trick to taking off the original fan. Take a heat gun and direct the flow of heat around the plastic fan and metal drive hub for about 15 seconds in a slow circular motion while holding the heat gun back enough as to not to burn or melt the plastic. We just want it hot enough to slightly expand.
Now with your five fingers, gently pry it up wiggling and it should come. If not put a little more heat until it does. Once the fan is removed, you can now see the front of the housing and the drive hub.
Give it a try or wait until I get the Ford instructions. Broken many of the original fans though on rebuilt units I've found those easy to pry off.