Clockwise from top: Hitachi alternator, original Lucas (flat) alternator fan, Hitachi (indented fan)
Hitachi fan. Not enough room for the grooved belt pulley.
Lucas fan: too large in diameter, so the mounting bolt is unreachable.
Ta da! A Volkswagen fan fits perfect. Right diameter, and correct depth, more than enough room for the big pulley.
making sure the spacer fits right in the middle with some JB Weld.
With the pulley installed.
Side view
Another view.