Alternator/Fan upgrade question

[74cookiecutter]

I have replaced the Alternator in my 74 with a 70amp Marchal Alt. It is probably from a lated 70s SC.
I have the proper fan housing and probably the correct Fan but when I tighten the pulley nut down the inside of the fan touches the Alt housing face.
The space between the back of the woodruf key and the Alt fan bearings is about 2mm. Should there be a washer or "shim" behind the Fan to keep it from touching the face of the Alternator?

My 50amp Marchal had a thick tapered washer/shim that was held in place by the woodruf key and I guess that it was there to keep the Fan from touching the Alt housing. It is way too thick to work on the 70amp alt though.

What gives????