Or just file the tab off as req'd, and keep an eye on the rest of the anode
.... which should be done anyway. FWIW, the replacement for my alpha does not
have the that tab ... what's important is that there be an anode, not it's
shape.

I have a 1995 19 ft cuddy with an Alpha 1 outdrive and rack & pinion
steering (not power steering). In searching for a new prop the Mercury
prop selector recommended an Alpha 4 20 pitch (48-834854A45) so I
bought one. When I went to put it on it clearly had more depth than
the current Black Max 19 pitch and hit the little sacrificial anode
steering tab or skeg (?) that sticks down on the outdrive behind the
prop.