Well, this may help. My initial fan spacer on my 64 1/2 was the standard spacer w/o AC. If I recall correctly, it did not measure up the same as what Bob Mannel had in his book (although I don't doubt his accuracy). It was, I believe, 3.20 inches even. A picture of it is below. You can see the thicker base that the non-AC spacers have.
A correct spacer for an AC car is also shown (the one I have now) and you can see that it has the thin base (as described in Bob's book).