I have done this on 2 trucks. I dont recall inner fender shims - attached direct to firewall. I dont recall shims between the inner and outer fenders at the top. Could be done, but none of the assembly manuals and lit I have reviewed has mentioned the shims you describe.
I dont have the dimension of the mounting hardware handy.
I longest vertical gap considered is the fender/door gap. I suppose that gap can be adjusted via extra/fewer washers at the rad support easy enough. There is also play in the cab-side bracket that the lower inner fender bolts to.
Let us know what you find once the new mounting hardware arrives - It should include the diagram for sequence.


~ HB
1966 Chevrolet K-10 | Ghost: formerly Flappy Fenders | In the Stovebolt Gallery
1962 Chevrolet C10
1962 Suburban