There was about an extra 1/4" of material on  the back of the casting which caused the alternator to sit too far forward, so I ground it down to where it's about flush with the other material around it. Once you have one of these alternators in your hand it is easier to see what I mean. Turns out I ground off too much, and the alternator then sat too far back, so I made up the difference with a thin washer.
Next you will be faced with the hole in the engine mounting plate being larger than the 3/8" hole in the alternator.
Positioning the alternator fore and aft