I just got out my service manual (I found it after doing my rebuild) and I have a picture showing that the official way of setting the timing marks is 'up'. The cam sprocket mark goes toward the top of the head. The crankshaft sprocket mark also goes to the top of the head. The book's wording makes it sound like it is as you said, as far as possible. Though as we have said, 180 out makes little difference. Both sparks fire simultaneously.
That said, the manual doesn't say much about the valve assembly. I will say that rotating the crank 360 won't change anything. When the pistons are at top dead center, you should have 2 valves closed on one piston (the power piston) and an exhaust valve just slightly open on the other. (Yes, even at TDC one valve is slightly open on one side. This is why the valve timing is so damn tricky). If you know which is the power piston, I would adjust both valves on this side simultaneously, then go 180, and do the two on the other. You can check for the power piston by pushing air through the exhaust of both cylinders at 180 or 360 to see which one seeps. That is provided they actually seal : p
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