If I'm clear on what you want to do, here is some info...
From the factory it should be a slotted head 10-32 pointed set screw which is about 1" long 89658-S7. Ford used the same set screw from 32 past 1940. all your going to see in the hole is the slot since the set screw is not long enough to be proud of the threaded hole. If all else fails to get it out there is only one way I am aware of and that is to heat the threaded section red hot inside the door. You want to be careful not to burn or blister the paint off the door skin. The slotted head of the set screw is easily broken off so make sure NOT to use a lot of force on it.
Here is a few pictures...It could also have a Allen set screw there.
Attachment 65765
Attachment 65766
Attachment 65767
Attachment 65768