JH valve timing

[wolfsbrg8v at bellsouth.net (wolfsbrg8v@bellsouth.net)]

Valve timing -- 1984 JH engine

The Bentley says to align the mark on the cam sprocket
with "upper edge of camshaft drive belt rear cover".

But I've also read that in the JH it's supposed to align
with the surface of the cylinder head.

What's the facts on this?

Thanks in advance --  Leo