The pipe you are having trouble with appears to be the fuel pre-heater connection. You should be able to leave the threaded fitting in the head. Just loosen all the connections on the pipe and pull it out of the head (it has an o-ring seal inside the fitting).

The tensioner is removed by simply undoing the larger of the two nuts (the one that is around the tensioner housing, and is actually a part of it.).

As for the head bolts, I can't remember off the top of my head what size they are, but they should be 12 point. Don't forget the 2 small allen head screws at the very front of the head (inside the chain "valley", in front of the sprocket. These are easy to forget!!)

Good luck!!

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‘84 300TD “Mountain Goat”
'62 300d Adenauer-350 Chevy - "Max"
'15 VW Passat TDI
'16 Dodge Ram 3500 - Cummins w/6-speed
'68 Mustang fastback
'55 T-bird
‘63 Studebaker Hawk