That will be metric and if you take that to someone with a bit of heat / gas bottles heat up the threaded part of the hub and that bolt will come straight out, this was a common problem with Ford's of that era, don't worry .
If I recall those bolts are soft and easily drilled out without gouging of damaging the threads I have done more of these on Sierra's Escort's and Orion's (front and rear on these two) than I care to remember when damper replacement was necessary all a very long time ago though