Thanks for all the suggestions on the Head removal.
I removed the screw plug on the tensioner with a 7/16" allen wrench and pulled out the spring.

Now I'm trying to take out the ring nut. It looks like a 12 point socket.
What size tool or allen wrench do I need to take that out?

P.S. Thanks for the tip on the 6mm bolt and 10mm nut for the guide rail pin. I think I understand that the you screw the bolt into the pin and the nut acts like a spacer to pull out the retaining pin.

Thanks again for anny suggestions.
Mike v