It may be a very early Greenfield, and they may have called it the HD8, then kept using the same model name when they began to make them with production tools later on.
I suggest you get the HD8 parts that are needed, put it together correctly, and begin making whatever other repairs are required once you've got it going well enough to see what else needs attention. It doesn't seem as if it will be a difficult project to get it working, and I think it will be a real show-stopper anywhere Greenfield enthusiasts can be found. It seems to be in really solid shape - you can have a lot of fun with it.
